National Institute of

Standards and Technology

Technology Administration

U.S. Department of 

Commerce

NISTIR 6796

MSEL

September 2001

FY 2001 PROGRAMS 

AND ACCOMPLISHMENTS

POLYMERS 

DIVISION
Advance measurement methods to characterize 

microstructure failure in composites

This optical image is a planar array of glass fibers 

embedded in epoxy resin matrix deformed under tension. 

The arrays are used to investigate the failure initiation in 

fibrous composites. In the optical image, the fibers are 

spaced (30 to 45) mm apart and the dark regions along 

each fiber are cracks that extend into the surrounding 

polymer matrix. The light blue regions that connect the 

fiber breaks show high deformation shear bands that 

emanate from the tips of the matrix cracks.
National Institute of

Standards and Technology

Karen H. Brown, 

Acting Director

Technology

Administration

U.S. Department of

Commerce

Donald L. Evans, 

Secretary

MATERIALS

SCIENCE AND 

ENGINEERING

LABORATORY

FY 2001 PROGRAMS 

AND

ACCOMPLISHMENTS

POLYMERS

DIVISION

Eric J. Amis, Chief

Bruno M. Fanconi, Deputy

NISTIR 6796

September 2001

ME

UNITED STATES OF AMERICA

DEPARTMENT OF COM RCE
ii

Executive Summary ............................................................................................................................................................. 1

Technical Highlights

Mass Spectrometry of Polyethylene ......................................................................................................................... 4

Combinatorial Study of Surface Pattern Formation ................................................................................................... 6

Measurement Methods Aid Development of Photoresists for Next-Generation Photolithography ......................... 8

Polymer Mass Distribution by Mass Spectrometry .................................................................................................10

Multi-Fiber Failure Propagation ...............................................................................................................................12

Biocompatibility of a Moldable, Resorbable, Composite Bone Graft .......................................................................14

The Mechanism of Sharkskin ...................................................................................................................................16

Projects and Programs

Combinatorial Methods .....................................................................................................................................................19

High-Throughput Measurements of Crystallization and Nucleation in Polyolefins ................................................20

Combinatorial Mapping of Polymer Film Wettabilty ................................................................................................21

Anisotropic Adhesion Between Polymers, Metals, Ceramics and Biomaterials ......................................................22

Patterned Polymeric Substrates for Directed Cell Growth ........................................................................................23

Microwell Arrays for Laser Capture Microdissection (LCM) ..................................................................................24

Tissue Development in Co-extruded Polymer Scaffolds ..........................................................................................25

Interface of Materials with Biology ....................................................................................................................................26

The Dynamic Effects of Protein Stabilization in Glass Forming Liquids ..................................................................27

Structure-Property Relationships in Dental Polymers ..............................................................................................28

A Moldable, Resorbable, Macroporous, Composite Bone Graft Containing Growth Factor ...................................29

Bioactive Polymeric Composites for Mineralized Tissue Regeneration ...................................................................30

Materials For Microelectronics ..........................................................................................................................................31

Characterization of Porous Low-k Dielectric Constant Thin Films ...........................................................................32

Polymer Fundamentals of Photolithography ...........................................................................................................33

Characterizing Buried Polymer/Substrate Interfaces ................................................................................................34

Materials For Wireless Communication .............................................................................................................................35

Dielectric Metrology for Polymer Composite Films in the Microwave Range ..........................................................36

Table of Contents
iii

Multiphase Polymeric Materials ........................................................................................................................................37

Constitutive Relationship of Polymer Blends for Process Modeling Needs ............................................................38

Modeling of Interfaces and Interphases of Polymeric Systems ...............................................................................39

Synergistic Interactions in Polymer-Nanoparticle Composites ................................................................................40

Structure-Property Characterization and Modeling .................................................................................................41

Mechanics of Fiber and Nano-Filled Composites ....................................................................................................42

Poly-OOF: A Virtual Experimental Tool for Polymer Research ..................................................................................43

Polymer Characterization ...................................................................................................................................................44

Optical Coherence Tomography ..............................................................................................................................45

Polyolefin Mass Spectrometry .................................................................................................................................46

Fluorescent Sub-Micrometer Probe Molecules with Starlike Architecture ..............................................................47

Standard Reference Materials ..................................................................................................................................48

Quantitative Mass Spectrometry of Synthetic Polymers .........................................................................................49

Support for the Biomaterials Integrated Products Industries...................................................................................50

Control of Extrusion Instabilities .............................................................................................................................51

Real-Time Process Monitoring ................................................................................................................................52

Micro-scale Processing ............................................................................................................................................53

Publications .......................................................................................................................................................................54

Staff and Organizational Structure

Polymers Division ....................................................................................................................................................62

Research Staff ..........................................................................................................................................................63

Organizational Charts ...............................................................................................................................................71

Certain commercial materials and equipment are identified

in this report in order to specify adequately the experimental procedures. In no case does such identification imply

recommedation or endorsement by the National Institute

of Standards and Technology nor does it imply necessarily the best available for the purpose.
1

Executive Summary

The Polymers Division provides measurement methods,

standards, and concepts to facilitate technology development, manufacture of products, commerce, and use of

synthetic polymers. Projects are selected based on assessments of current needs and in anticipation of future needs

as determined from topical workshops, industry roadmaps,

as well as visits to companies and other research organizations. Much of our work is performed collaboratively with

customers. Over 35 companies, in addition to trade associations and other federal agencies participated in the

work of the Division. The close interactions with customers assure that the work remains focused.

The work of the Division is organized into three groups

that focus on areas where synthetic polymers are exploited

for their unique properties—electronics materials, lightweight structural materials, and biomedical materials. Two

other groups are concerned with needs that crosscut the

applications areas—better control of polymer processing

and more rapid test methodology.

• The Division is building on the success of its effort to

characterize properties of porous thin films under development as low-k dielectrics for use as interlevel

dielectric films in the next generation IC chips. The new

metrology we have developed received strong endorsements by both International SEMATECH and the National Research Council panel performing a crosscutting assessment of NIST programs in microelectronics.

In anticipation of the needs of the microelectronics

industry for measurement methods to identify characteristics of photoresist polymers that limit further reductions in feature size, the Division successfully used

neutron scattering to elucidate the shape of features

produced by photolithography. Other measurement

strategies are under development to determine how

macromolecular dynamics and other molecular characteristics are affected by the thickness of polymer thin

films of the sort used in today’s photoresists.

• For structural applications polymeric materials are combined in manufacture with other materials, particulates,

fibers or other polymers to achieve property enhancement, cost reduction and/or improved processibility.

Although many successful products have been developed it is recognized that future progress rests on

improving predictions of resultant properties from

constituent properties, particularly at the molecular

level. Our work in this area builds the connections

between computer simulations of molecular behavior

and macroscopic properties. This year we developed a

new instrumental method that characterizes how fracture of a single glass fiber affects failure processes of

neighboring fibers and the matrix resin in a fiber-reinforced composite.

• Increasing use is made of synthetic polymers in human

implants to restore body function and improve quality

of life. New therapies are under development through

tissue engineered products approaches. This year we

demonstrated the utility of a new approach to produce

a polymeric scaffold of controlled morphology by

coextrusion of incompatible polymers followed by

leaching of one polymer to provide three-dimensional

connected pores. Workshops this year with providers

of medical products and services identified a prioritized

list of needed reference biomaterials and data. The

Division has responded by issuing the first NIST reference biomaterial for orthopedic applications, a medical

grade polyethylene that will be used for comparative

studies and for developing improved materials.

• The Polymers Division is pioneering the development of

combinatorial methods to measure rapidly properties of

materials. The approach is similar to that used with a

great deal of success in the pharmaceutical industry in

discovery of new drugs. The key components of a

combinatorial method are a sample in which composition, film thickness or other characteristics are controlled, a technique to image the entire specimen for

properties of interest, optical microscopy, for example,

and analysis techniques capable of treating exceedingly large amounts of data. We have reported successes in each aspect of the combinatorial process,

most notably development of a method of imaging

polymer adhesion for a polymeric library. Not only has

it been demonstrated that the combinatorial approach

can greatly reduce measurement time, but we have also

observed new phenomena in several experimental systems including the structure of thin films of block copolymers.

• The Polymers Division has a sustained effort in developing methods to measure polymer properties during their

processing. The initial application was in measurement

of temperature in the resin, rather than in the processing equipment as is traditionally done. This work

showed that the resin temperature was frequently much

higher than that given by the traditional temperature

method. This sensor work has been extended to measurement of polymer orientation that is of particular

interest in film blowing. Other optical methods have

been developed to elucidate the origins of “sharkskin”

surface imperfections in extrusion of polyolefins. With

these tools better control of polymer processing and

strategies to improve end products are made possible.
2

• The Division’s work to

establish matrix-assisted laser desorption/ionization mass

spectrometry (MALDI

MS) as a quantitative

tool for synthetic

polymers advanced

this year with the

successful completion

of an inter-laboratory

comparison with 23

institutions. For the

first time, NIST has

provided the MALDI

MS of polystyrene

Standard Reference

Material 2888. Of particular significance, we

have overcome the

ineffectiveness of

conventional methods

of cationization of

polyolefins and demonstrated the mass

spectroscopy of polyethylene by a covalent

cationization method.

Although this polymer

type dominates the

synthetic polymer

market, determination

of their molecular mass and molecular mass distribution

has been difficult and not quantitative.

In looking forward to next year, several significant advances can be anticipated. Our pioneering work demonstrating high throughput experimental methods will be

given a new home in an extensively remodeled laboratory

and with the initiation of an industrial consortium, the

NIST Combinatorial Methods Center. Another laboratory

remodel will provide facilities to initiate a new program in

metrology for tissue engineering that includes collaborations with the NIST Biotechnology Division and two

institutes at the National Institutes of Health. Both of

these projects have received support from the NIST competence building program after success in the 2000 and

2001 competitions. In

polymer processing we

will focus on new measurement technology

that will provide the

ability to control extrusion instabilities of

sharkskin and gross

melt fracture. In the

microelectronics area we

are working to develop

an extension of our

porous thin films measurement method that

can be implemented in

the industrial laboratory

without the need for

access to our specialized neutron and x-ray

facilities.

Among the principal

outputs of the Division

are technical publications; the number of

papers published is the

highest among all NIST

Divisions. Every year in

our annual report we

provide a list of publications for the past year.

The Division also issues a CDROM of its publications for each calendar year.

To provide more timely access to our technical publications, the publications are also being organized for distribution on the Division web site. The collection is organized by research group, keywords from the papers, and

a set of subject terms that correspond to current thrusts

in polymer science and technology. The most recent version of the Polymers Division web site is available at

http://www.nist.gov/polymers.

The first year of the 21st century has been an excellent

one for the Polymers Division as we have also enjoyed the

celebration of the NIST Centennial. I hope this annual

report provides a useful overview of our activities. We are

always pleased to provide more details. Feel free to contact us for more information.

Eric J. Amis

Chief
3

Technical Highlights

The following Technical Highlights section includes expanded descriptions of research projects that have broad

applicability and impact. These projects generally continue for several years. The results are the product of the

efforts of several individuals. The Technical Highlights

include:

• Mass Spectrometry of Polyethylene by the “Covalent

Cationization Method”

• Combinatorial Study of Surface Pattern Formation in

Thin Block Copolymer Films

• Measurement Methods Aid Development of Photoresists for Next-Generation Photolithography

• Polymer Mass Distribution by Mass Spectrometry

• Multi-Fiber Failure Propagation

• Biocompatibility of a Moldable, Resorbable, Composite

Bone Graft

• The Mechanism of Sharkskin
Technical Highlights

4

Polyolefins dominate the synthetic polymer market. While

they have a very long production history, new developments in metallocene catalysts have caused a great resurgence of activity resulting in a wide variety of new applications and increased material production. The new

catalysts can provide unprecedented control of polymer

molecular mass and molecular mass distribution, copolymerization control, stereochemistry, etc. Molecular mass

distributions of polyolefins currently are determined by

gel permeation chromatography, a method that requires

calibrations by mass standards. Such standards do not

exist for these new types of polyolefins, thus crude approximations are used that introduce large uncertainties.

MALDI has provided valuable information on the nature

of the polymerization process and the resultant structure

for many other polymer types, but not for polyolefins. If

polyolefins could be routinely analyzed by MALDI, development time for new catalysts and polymers could be

greatly reduced.

Synthetic polymer cationization by metals such as sodium,

potassium, silver, copper, etc., involves association of

cations with functional groups on the polymer. Examples

of functional groups include the carbonyl groups of methacrylate polymers, the double bonds of diene polymers,

and the phenyl groups of styrenics. Polymers that lack

polar, unsaturated, or aromatic groups cannot be analyzed

by MALDI. Thus, polyolefins (polyethylene, polypropylene, polyisobutylene, poly(methyl pentene), etc.) are

excluded.

A chemical modification method has been developed in

the Polymers Division that allows mass spectrometry to be

performed on these materials for the first time. Two synthetic steps are involved: bromination of the polymer,

followed by conversion of the brominated site to a

charged ammonium or phosphonium group. Here we give

results for a low mass fraction of a commercial polyethylene: NIST Standard Reference Material, SRM 2885. The

bromination reaction employed brominates sites of

carbon-carbon double bonds, present in low concentration in many commercial polyethylenes. The content of

carbon-carbon double bonds of structure RCH=CH2

 (vinyl) of SRM 2885 is determined from Fourier-transform

infrared spectroscopy. The determined value, (0.125 ± 0.01)

Mass Spectrometry of Polyethylene

by the “Covalent Cationization Method”

Saturated hydrocarbon polymers, polyethylene and polypropylene, are the most widely used of all synthetic polymers.

Their molecular mass and molecular-mass distribution (MMD) are critical in determining processing and performance

properties. Mass spectrometry is currently the most promising method for obtaining accurate absolute MMDs; however,

polyethylene and other polyolefins have not been amenable to mass spectrometric characterization due to the ineffectiveness of conventional methods of cationization. A new method has been developed in which an organic cation is

covalently bonded to the polymer to produce the necessary ionization for successful matrix-assisted laser desorption/

ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS).

C=C per 100 C, corresponds to approximately one vinyl

group for every 2 molecules as estimated from the certified

mass average molecular mass of 6280 g mol-1 and a polydispersity of 1.13. The vinyl content is reduced by bromination to 0.32 ± .03 of its original value. Next, the brominated polymer is treat with tri-phenyl phosphonium (TPP).

Using integrated intensities from alkyl benzenes the phenyl content in TPP-treated polyethylene is estimated to be

0.27 phenyl/100 C, or 2 per original vinyl group, approximately. Since each phosphonium group contains 3

phenyls and the reaction yields one phosphonium group

per reacted vinyl the qualitative results are in agreement

with the observation that approximately one-third of the

original vinyl groups remain unreacted by the treatment

employed here. Hence, an estimated one-third of the original polyethylene molecules are labeled with TPP by the

chemistry employed.

The figure above shows the MALDI-TOF-MS results

from SRM 2885 that has been modified by the covalent

cationization method. No smoothing or baseline subtraction was used in the data presented. A strong MALDI

signal was produced from the modified polymer while the
 Technical Highlights 

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5

unmodified and the brominated polymer produced no

signal at all. Oligomers are clearly present up to 7000

g mol-1, higher than ever observed before for intact,

saturated-hydrocarbon oligomers by mass spectrometry.

Current work centers on extending the mass range to

higher values more representative of commercial polymers.

The mass spectrum of SRM 2885 shows a strong repeating

pattern of 28 g mol-1; however, a pronounced repeat of

14 g mol-1 is also apparent. This may be due to fragmentation of the polymer in the mass spectrometer or may be a

consequence of the polymerization chemistry of olefins.

The abundance of tightly spaced peaks with 14 g mol-1

spacing below 3000 g mol-1 suggests the existence of

fragmentation. However, these peaks also exist at the very

high mass end of the spectrum above 6000 g mol-1. It is

known that premature chain termination can produce

molecules with an odd number of carbon atoms and thus

W.E. Wallace, B.J. Bauer (Polymers Division, NIST)

Bauer, B.J., Wallace, W.E., Fanconi, B.M., Guttman, C.M. “Covalent Cationization

Method” for the Analysis of Polyethylene by Mass Spectrometry. Polymer 42,

9949–9953 (2001).

can give a repeat spacing of 14 mol-1. It is possible that

both of these two effects may be occurring in this mass

spectrum.

While simple modification of as-polymerized polyolefins

with bromine and TPP represents a model case, the covalent cationization method applies to other chemistries and

polymer types as well. Many other types of chemistry

other than functionalizing vinyl groups are possible. For

example, hydroxy-terminated polystyrene, polybutadiene,

and hydrogenated polybutadiene (fau polyolefin) have

been modified by converting the hydroxy to bromide by

treatment with PBr3

 and then converting to –N+(CH3)3 or

–P+(C6

H5)3 by treatment with trimethyl amine and TPP

respectively. The figure on the left shows a hydroxyterminated hydrogenated polybutadiene covalently

cationized with tri-methyl ammonium. The spectrum shows

excellent resolution and low background making it ideal to

determine molecular-mass distribution. Conventional metal

cationization methods fail for this material even though

oxygen is present in the end group because the oxygen is

in such low abundance that metal cationization becomes a

very unlikely event. Covalent cationization overcomes this

by chemically adding a charge to each chain.

Industry Interaction:

Efforts to expand the MALDI technique to nonpolar

polyolefins are in progress. Major product monitoring

cost- and time-savings should accrue to industrial

polyolefin suppliers and users with this technique when

perfected.

Board on Assessment of NIST Programs, National

Research Council
Technical Highlights

6

Combinatorial Study of Surface Pattern Formation

in Thin Block Copolymer Films

Figure 1. True color optical micrographs of a PS-b-PMMA

film having a gradient in thickness from 63 nm to 117 nm.

The addition of three successive lamellae to the surface is

shown.

Block copolymers are amphiphilic polymer materials composed of two different polymers joined by a covalent bond.

This linkage of chemical functionality inhibits phase separation of the polymers beyond a molecular scale and makes

these materials useful as stable elastomers, adhesives, and

as surfactants stabilizing polymer blends against phaseseparation. The tendency of block copolymers to selforganize into ordered nanoscale patterns in bulk and in thin

films has also led to recent intense interest in using these

materials as templates for nanoscale arrays in thin films and

photonic devices. Block copolymer films exhibit seemingly

stable surface patterns over large-length scales (tens of

micrometers) whose origins are not understood, but

which provide an attractive methodology for forming

surface patterns of tunable dimension. We determine, by

combinatorial high-throughput approach, the range of

morphology types that arise through self-organization in

these films and the factors that influence their size and

stability. The high information content generated by the

combinatorial (“combi”) method revealed surface pattern

types overlooked in the past and the phenomenology

governing the size of these patterns. The combi results on

self-organization in such systems should be helpful to

understand the physical origin in terms of competition

between micro phase-separation and surface elasticity,

and the fundamental nature of molecular interactions

between the components of the block copolymer and with

surfaces.

Previous studies of surface pattern formation in block

copolymer films have not yielded a predictive theory that

quantitatively relates the phenomena to molecular parameters. Among questions about basic phenomenology,

factors governing the size of the island and hole patterns

(e.g., molecular mass M and temperature T) in these films

are not well understood. Notably, the size of these patterns

is often large in comparison to the lamellar spacing Lo

 (or

even film thickness h) so that the molecular interpretation

of these patterns is subtler than ordering in bulk block

copolymer materials. The precise thickness range in which

the films remain smooth is another basic film property that

requires further investigation. Since these film properties

are crucial for the development of a theoretical description

relating the self-organizing process to fundamental moUnique properties of block copolymers in melts, blends and solutions lead to their use as adhesives, emulsifying agents,

thermoplastic elastomers, compatibilizers, etc. Many applications exploit the ability of these materials to self-organize

into ordered structures in bulk and in thin films. The nature of interactions in block copolymer systems is determined by

exploiting the ability of block copolymers to form quantized periodic structures in thin films that directly reflect molecular parameters such as block lengths, chemical interactions between block constituents, and interactions with inorganic

substrates. Combinatorial gradient methods are used to validate a vast body of existing literature and simultaneously

discover new knowledge reflecting the influence of different molecular parameters on entropic, enthalpic and kinetic

relationships in block copolymers.

lecular interactions in the system, we have investigated

pattern formation in block copolymer films using combinatorial methods on films produced by a flow-gradient technique to have a range of h and M.

Near symmetric poly(styrene-b-methyl methacrylate) (PS-bPMMA) diblock copolymers with different M were used to

prepare thickness gradients on Si wafers. The wafer was

attached to a robotic stage and a small amount of solution

spread under a suspended knife-edge at constant acceleration to form a thickness gradient. Film thickness was measured using an automated UV-visible interferometer. For the

current experiments, up to four PS-b-PMMA gradient films

were placed on the same wafer and annealed at 170 °C under vacuum to allow ordering of the block copolymers.

Optical microscopy and atomic force microscopy (AFM)

were used to characterize the surface patterns. Previous

studies showed that when PS-b-PMMA is cast and annealed on a Si substrate the PMMA preferentially segregates to the substrate while the PS segregates to the air

interface. The limited data in literature from individual

(single-thickness, single molecular mass) film studies suggests that this behavior produces smooth films for thick-
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P.A. Smith, J.F. Douglas, E.J. Amis, A. Karim (Polymers Division, NIST)

Smith A.P., Douglas, J.F., Meredith, J.C., Amis, E.J., Karim A. Combinatorial Study

of Surface Pattern Formation in Thin Block Copolymer Films, Phys. Rev. Lett., 87,

015503, (2001).

Smith A.P., Douglas, J.F., Meredith, J.C., Amis, E.J., Karim A. High-Throughput

Characterization of Pattern Formation in Symmetric Diblock Copolymer Films.

J. Poly. Sci. Polym. Phys. 39, 2141 (2001).

Figure 2. AFM micrographs (white corresponds to higher

topography) of a PS-b-PMMA gradient film at different

thicknesses showing: (a) the smooth morphology; (b and

c) islands; (d) labyrinthine pattern; and (e and f) holes on

the surface of the films.

ness ranges near the characteristic values that are halfinteger multiples of lamellar spacing, Lo, while hole and

island patterns form when the film thickness deviates substantially from the characteristic values.

An example of the morphological change in the block copolymer films as a function of h is shown in Figure 1. This

image shows optical micrographs of a 26k PS-b-PMMA

(Lo

 = 17 nm) continuous gradient film with a thickness range

of » 54 nm corresponding to the addition of three lamellae

layers. The morphology evolves from smooth to islands to

labyrinthine to holes to smooth as the film thickness increases. The regions of hole and island pattern formation

are consistent with previous observations on films of fixed

thickness, but the observation of the broad smooth regions

and the labyrinthine morphology are novel. Figure 2 shows

AFM micrographs of the surface patterns at higher magnification. The film is smooth for the thinnest film, with islands

forming as h increases that coalesce into a labyrinthine

pattern. For even greater h a continuous lamella with hole

forms. These morphological trends are observed for all M

and thickness range up to 6.5 Lo

. The importance and implications of the novel observations are discussed below.

The observation of the broad smooth regions implies a

change in film thickness across this area where the block

chains of styrene and methyl methacrylate can stretch up to

a maximum of 14 percent with increase of film thickness, or

contract down to a minimum of 14 percent with decrease of

film thickness, without forming additional layers. These

maximum and minimum limits of extensibility are novel

results that will be useful in developing a theoretical understanding of the relative importance of entropic (chain

stretching) versus enthalpic (chemical interaction parameter) factors in block copolymers. The results on limits of

extensibility are also found to be nearly invariant with

molecular mass thus generalizing the phenomena. No

statistically significant variation in this value was found

with increasing h up to the maximum of » 6.5 Lo tested,

indicating that height variation is confined to the outermost lamella that is another novel observation. We attribute the height variation resulting from chain deformation in the outermost surface lamella to the kinetics of the

ordering process.

The kinetics of the self-organization process can be measured by the continuous gradient approach as well, as

demonstrated for the structural evolution of the novel

labyrinthine regime. This was obtained by measuring the

dependence of the pattern size on M at different times.

The scale (1) of the patterns decreases with an increase in

M (a non-intuitive result), yielding the relationship λ (mm)

~ M-1.65. This behavior is attributed to the increasing surface elasticity of the block copolymers with increasing M

that serves to inhibit formation of large surface features.

In summary, combinatorial methods have been successfully applied to observe novel morphologies and to establish fundamental kinetic relationships in the ordering properties of block copolymer films. These results agree well

with existing non-combinatorial literature data on the same

systems, validating the combinatorial approach and the

continuous gradient method. The results will enable developing a theoretical understanding of key questions in

block copolymers such as the nature of interactions between blocks, as well as block interactions with different

materials. The investigative combinatorial tools and methodologies developed will accelerate research in practical

application areas of block copolymers such as

compatibilization, adhesives, etc., in the future through the

development of a NIST Combinatorial Methods Center.

“This...is an excellent example of using a clever (combinatorial) trick to extract new and important insights

from what even the authors admit is a well-studied system. Well done!”—Physical Review Letters Manuscript

Review
Technical Highlights

8

Measurement Methods Aid Development of

Photoresists for Next-Generation Photolithography

Photolithography, the process used to fabricate integrated circuits, is the key enabler and driver for the semiconductor

industry. As lithographic feature sizes decrease to the sub-100-nm length scale, significant challenges arise because the

feature size is reaching the limits of current structural characterization methods. In addition, both the image resolution

and the thicknesses of the imaging layer approach the inherent macromolecular dimensions characteristic of the polymers used in the photoresist film. Unique high-spatial resolution measurements are developed to understand the materials and processes challenges facing the development of photoresists for next-generation sub-100-nm lithography.

Photolithography

Photolithography remains the driving

technology in the semiconductor industry

to fabricate integrated circuits with ever

decreasing feature sizes. There are significant challenges in extending this technology to fabricate the smaller feature sizes

(sub-100 nm) needed to continue performance increases in integrated circuits. To

succeed, the critical dimensions (CD) of

the lithographic structures must be controlled to within 10 nm. An increasingly

difficult challenge lies in measuring structural parameters (feature size, shape and

quality) over these length scales. Further,

new radiation sources with shorter wavelengths (193 nm and 157 nm) require photoresist films less

than 100-nm thick to ensure optical transparency and

uniform illumination. In these ultrathin films, confinement

can induce deviations in several key materials parameters

such as the macromolecular conformation, glass transition

temperature, viscosity or transport properties. It is not yet

clear how deviations due to confinement will affect the

ultimate resolution in these ultra-thin photoresist films.

To advance this key technology, we work closely with

industrial partners including IBM, Shipley and Brewer

Science to develop unique high-spatial resolution measurements to better understand the lithographic process,

to guide the development of materials, and to provide

high-quality data for key model photoresist systems

needed in advanced simulation packages. We have made

significant advances in two areas, a new method for the

structural characterization of lithographically prepared

structures and the first measurements of the atomic-level

dynamics of polymers in ultrathin films.

Structural Metrology with SANS

As feature sizes continue to decrease with dimensions

approaching 100 nm, the allowable resolution limits of the

lithographic process become more stringent and difficult

to measure. The precise measurement of the size and quality of lithographically prepared features as they decrease

in size is critical for evaluating and improving new lithographic processes and materials. Current microscopybased techniques such as scanning

electron microscopy (SEM) and atomic

force microscopy often require specialized modifications to enable the measurement of either the critical dimension

or feature resolution parameters. More

importantly these techniques become

extremely challenging as feature sizes

continue to decrease.

We have demonstrated the powerful use

of small-angle neutron scattering (SANS) to quickly, nondestructively, and quantitatively characterize both the size

and profile of lithographically prepared structures as prepared on a silicon wafer substrate. Until recently, SANS

instruments were unable to measure lithographic feature

sizes (sizes greater than 300 nm) and neutron beam fluxes

were insufficient to measure scattering from thin-film

structures. Today, the high-intensity NIST Center for

Neutron Research (NCNR) neutron source, new focusing

optics, and smaller lithographic features allow for the

SANS measurements. Other important advantages include:

a) the measurement of structures on silicon because single

crystal silicon wafers are transparent to neutrons; b) a

measurement metric averaged over an area of several cm2

;

c) less stringent SANS instrument requirements as lithographic structures decrease in size; and d) no need for a

calibration standard.

We have demonstrated the SANS metrology through an

analysis of the scattered intensity from a periodic grating

structure (figure above) with a nominal linewidth of

150 nm. In the SANS data, up to six orders of diffraction

peaks are observed. The position and intensity of these

peaks provide measures of CD and the cross-sectional

shape with nanometer resolution. SANS measurements

may serve as a powerful tool to validate calibration standards and is one of very few methods able to provide

high-resolution metrology for the evaluation of new materials and processes for structural features expected to be

smaller than 100 nm in size.

Figure 1. Top-down and edge-on SEM

images and two-dimensional SANS data

from several periodic grating patterns

with 150-nm linewidths.
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Local Polymer Dynamics

Current photoresists use a photogenerated acid catalyzed

deprotection reaction on the polymer to produce a solubility change in exposed areas. The local, atomic-level, dynamics of the photoresist polymer directly affect transport

processes essential to modern photoresists, such as the

diffusion of photogenerated acids and other small molecules within the polymer matrix. To date, changes in the

local dynamics of polymer thin films have been inferred

from changes in macroscopic quantities such as the apparent glass transition temperature, Tg, as a function of film

thickness and substrate interaction energies. Direct measurements of the segmental motions of polymer chains

confined to ultrathin films will provide a molecular picture

of observed changes in these macroscopic quantities and

insight into differences in photoresist transport processes

in ultrathin films. By using different polymers and polymer/substrate combinations, we obtain crucial insight into

the dynamical effects of polymer thin-film confinement.

E.K. Lin, C.L. Soles, W.L. Wu (Polymers Division, NIST)

Wu, W.L., Lin, E.K., Lin, Q.H., Angelopoulos, M. “Small Angle Neutron Scattering

Measurements of Nanoscale Lithographic Features,” J. Appl. Phys., 88, 7298 (2000).

Soles, C.L., Lin, E.K., Lenhart, J.L., Jones, R.L., Wu, W.L., Goldfarb, D.L., Lin, Q.,

Angelopoulos, M. “The Effects of Thin-Film Confinement on the Thermal Properties

of Typical Deep-UV Photoresist Resins,” submitted to J. Vac. Sci. Tech. B. (2001).

Incoherent neutron scattering at the NCNR High Flux

Backscattering Spectrometer was used to directly probe

the atomic and segmental motions of polymer films as thin

as 75 Å on silicon substrates for the first time. This technique characterizes motions on a frequency scale of

200 MHz or faster in terms of a mean-square-displacement

<u2

>. We find that thin-film confinement generally diminishes <u2

>, irrespective of the polymer/substrate interactions. The degree to which <u2

> is suppressed appears to

depend on the level of vibrational anharmonicity in the

polymer. Strongly anharmonic polymers show larger decreases in <u2

>, particularly below the bulk Tg. For example, the protected (before exposure) photoresist polymer shows a high level of mobility (large <u2

>) below the

glass transition that is suppressed strongly by confinement. However, the deprotected version of this polymer

shows a much lower level of sub-Tg mobility (primarily

harmonic motions) with very little effect from confinement

(Figure 2). The markedly different behavior between related polymers provides important insight into the dependence of photoresist properties on the chemical structure

of the polymer, information important to photoresist

designers.

“The continuous miniaturization of semiconductor devices poses many challenges to lithography...One of

these challenges is to measure precisely the size, shape

and quality of the circuit patterns. The SANS method is a

new technique to measure lithographic patterns [and]

capitalizes on the unique capabilities at NIST...”

Q. H. Lin—IBM T. J. Watson Research Center

“The gate CD [critical dimension] control requirements

for the 130-nm node and below are also among the most

difficult challenges [for lithography]. Advances in process control, resist materials, line edge roughness and

metrology will be necessary to achieve less than 10-nm

CD control.”

1999 International Technology Roadmap for

Semiconductors.

Figure 2. Mean-square displacement, <u2>, as a function

of temperature for a protected polymer (PBOCSt) and a

deprotected polymer (PHS) for both the bulk material and

10-nm films.
Technical Highlights

10

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) is a new method of polymer analysis that works well for biopolymers, proteins and nucleic

acids, that are essentially of single mass (excluding isotopic effects). The situation is quite different with synthetic

polymers owing to the presence of a distribution of

masses that not only spreads the signal over a range of

masses corresponding to the polymer’s mass distribution,

but also invokes questions of how the signal at the detector is affected by having a distribution of masses. As

preliminary to developing a research program that addresses issues of how sample preparation, laser intensity,

instrument parameters and detector response may be

affected by mass distribution, NIST organized and led an

inter-laboratory comparison to determine the current

status of measurements and began a dialog on quantitative mass spectrometry of synthetic polymers.

The inter-laboratory comparison was designed in consultation with the American Society of Mass Spectrometry Working Group on Synthetic Polymers. Membership in this special interest group represents many

industrial laboratories, including those of major producers of synthetic polymers. Samples of wellcharacterized low-molecular mass polystyrene were

sent to any institution requesting it.

The polystyrene was custom synthesized to specifications provided by NIST to insure that the number

average molecular mass could be determined by highresolution nuclear magnetic resonance (NMR) and the

mass average molecular mass by light scattering. These

values by classical methods were used to compare

moments calculated from the MALDI mass spectrum.

One end of each polystyrene molecule contained a t-butyl

group that was not only detectible by NMR but also was

useful in assessing the quality of end group determinations by MALDI MS.

Polymer Mass Distribution by Mass Spectrometry

Molecular mass distribution is the characteristic that most affects processing and properties of polymers. However, in

absence of absolute methods for measuring mass distribution, methods that require calibration must be used. Owing to

the lack of suitable calibration standards for most polymers, alternative methods of determining mass distribution are

sought. Mass spectrometry is an absolute method for determining mass of molecules of essentially single mass. With

recent advances the method may work for synthetic polymers, as well, provided that the signal strength depends on

mass in a predictable manner. An inter-laboratory comparison of analysis of polystyrene by mass spectrometry has been

completed with the objective of assessing the current status of the method and evaluation of how moments of the measured mass distribution compare to those determined with classical methods.

A total of 23 institutions participated in the inter-laboratory comparison (10 industrial, 9 academic and 4 government laboratories). NIST Polymers Division also characterized the polymer by NMR for Mn and by light scattering

for Mw.

Fourier transform infrared spectroscopy confirmed the

presence of the t-butyl end group, as anticipated by the

synthesis method. Size exclusion chromatography was

used to insure vial-to-vial homogeneity in the samples

distributed to participants. Each participating laboratory

was asked to perform MALDI mass spectrometry using

two distinct protocols, one prescribed and the other left to

the discretion of the participants.

Figure 1. Mass spectrum of polystyrene used in

interlaboratory comparison by MALDI MS.
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Participants were instructed to report their mass spectra as

well as moments of the mass distribution. The latter request was used to assess the status of analysis software,

which is largely provided by MALDI MS instrument

manufacturers.

Analysis of the moments reported by the participants

revealed inconsistencies among laboratories in calibrating

instruments. These inconsistencies also affected determinations of end group mass. By compiling all the reported

spectral data (as opposed to reported moments) using

both protocols into one analysis it was found that MALDI

ToF MS returned an Mn

 of (6610 ± 100) g/mole and an Mw

of (6740 ± 90) g/mole, uncertainties are standard uncertainties. These numbers were below those of the classical

methods, but still within the overlapping uncertainty

ranges. Detailed results of this study have been recently

published in Analytical Chemistry.

The polystyrene used in the inter-laboratory comparison

will be available as Standard Reference Material (SRM)

2888, certified for mass average molecular mass by light

scattering. The NMR determined number average mass

and the MALDI MS data, including the full mass spectrum, will also be available as supplemental data. This is

the first polymer molecular mass standard to have its mass

distribution presented. Although polystyrene calibrants

for gel permeation chromatographs are readily available,

this new polystyrene SRM demonstrates the potential of

MALDI MS for mass distribution measurements in synthetic polymers.

C.M. Guttman, B.M. Fanconi (Polymers Division)

Guttman, C.M., Wetzel, S.J., Blair, W.R., Fanconi, B.M., Girard, J.E., Goldschmidt,

R.J., Wallace, W.E., VanderHart, D.L. NIST-Sponsored Interlaboratory Comparison

of Polystyrene Molecular Mass Distribution Obtained by Matrix-Assisted Laser

Desorption/Ionization Time-of-Flight Mass Spectrometry: Statistical Analysis.

Analytical Chemistry, 2001, 73, 1252-1262.

The establishment of a standard method for determination

of mass distribution by MALDI MS will facilitate its acceptance as a new method. Owing to the importance of

mass measurements within the polymer industry, analytical

laboratories that serve the industry and research laboratories in general, an effort was initiated to develop a standard measurement protocol for mass measurements by

MALDI MS. A new technical working activity, TWA 28,

was formed under the auspices of VAMAS, the Versailles

Project on Advanced Materials and Standards. Laboratories in five countries, Canada, Italy, Germany, Japan and

the United States are engaged in developing a measurement protocol for analysis of the mass distribution of

polystyrene by mass spectrometry. The framework of the

proposed measurement method will be the sample preparation and measurement outline used in the inter-laboratory

comparison augmented to reflect knowledge gained in the

analysis of the inter-laboratory comparison. Although the

measurement uncertainty of the inter-laboratory comparison was much less than common with classical methods

no estimate could be made of systematic uncertainties,

type B.

An assessment will be made of possible sources of systematic uncertainty. Collaborative research will be undertaken to reduce sources of uncertainty, where possible.

“NIST develops standards for MS of polymers...important

because mass distribution of synthetic polymers affects

processing and properties.”

C & E News 6/11/2001
Technical Highlights

12

The implementation of advanced materials in structural

applications is often hampered by the inability of the

design engineer to predict reliably failure behavior, failure

strength, fatigue behavior, energy absorption characteristics, and mechanical response of the composite part

to multi-axial loading conditions. Because of their complex

architecture, composites are

analyzed on many different

scales, with micro-mechanics

and macro-mechanics being

two broad classes. Micromechanics provides information

about non-averaged localized

properties (e.g., constituent

deformation and stresses and

localized failure behavior—

fiber, matrix and interphase).

Qualitatively these localized

properties have been shown to

strongly influence the performance properties of the composite. In contrast, macromechanics analyses, which are used at the lamina level

and higher, use average strength and stiffness properties

and failure criteria defined by average stresses and overall

lamina strengths. Although the latter approach is

computationally expedient, it fails to predict the effect of

microstructure changes on composite failure behavior.

The goal of our work is to provide the necessary links

between macro-mechanics approaches and micromechanics properties. For reliable prediction of composite

performance properties, non-averaged micro-mechanics

properties that account for the composite environment

must be included, while keeping the computational process tractable. The microstructure of the composite lamina

is being used to guide the selection of appropriate micromechanics experiments and analysis techniques to obtain

micro-mechanics parameters. Initially, we use 2-D multifiber arrays in experiments to quantify the interaction

between fibers during fiber fracture, constituent deformation behavior in the composite environment, and the localized failure behavior of the fiber, matrix and interphase

region.

Multi-Fiber Failure Propagation

With the increasing use of advanced composites in structural applications, understanding how to predict and manage

failure in composite structures has become a critical problem. As noted by the Automotive Composite Consortium, there

is a major need to generate relevant materials property data that can be used in a computational program by design

engineers to predict composite performance. In response to this need, test methodologies and a tow-based modeling

program are being developed to facilitate the seamless integration of critical materials data into composite analyses.

Results are shown in Figures 1 and 2, where fiber fractures

with debonding and associated matrix crack formation are

illustrated for a 2-D multi-fiber array composed of E-glass

fibers embedded in diglycidyl ether of bisphenol-A

(DGEBA) epoxy resin cured with meta-phenylene diamine

(m-PDA). Although the interfiber spacing, φ, is less than

Figure 1. Fiber break patterns from E-glass/DGEBA/

m-PDA 2-D multi-fiber array immediately after removing

stress. The interfiber spacing is denoted by φ.

Figure 2. Fiber break patterns from E-glass/DGEBA/

m-PDA 2-D multi-fiber array 24 h after removing stress.

The interfiber spacing is denoted by φ.
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13

mation. Although the origin of these deformation regions

are not clearly understood, 45-degree deformation bands

emanating from the matrix cracks during the test under

tensile conditions have been observed.

Using the same constituent composition, fiber fracture in a

multi-fiber specimen with the fibers touching is shown in

Figure 3. In this specimen, matrix crack formation has been

suppressed, and clustering of the non-aligned fiber breaks

is observed. The extensive matrix damage around the fiber

breaks occurred when the applied stress on the specimen

was removed. However, the absence of this type of deformation in the non-touching 2-D array (Figure 3), suggests

that the matrix deformation is higher surrounding the fiber

breaks in the touching fiber specimen. In addition, this

matrix damage along with the location of each fiber break

has been observed by optical coherence tomography

(OCT).

Capitalizing on the ability of OCT to see changes in the

deformation state in the resin, residual stresses have been

observed in 2-D multi-fiber specimens. These stresses may

influence the observed failure behavior.

In previous research on single-fiber specimens we have

noted that the matrix is non-linear viscoelastic. However,

reconciling this effect with the occurrence of brittle fracture in composite specimens has been problematic. A 2-D

multi-fiber array specimen was taken in several steps to a

strain level that induces fiber fracture. During a period of

5 min, numerous nonaligned fiber breaks occur

in the observation region,

reflecting the role that the

matrix has on the stress

redistribution process in

adjacent fibers after fiber

fracture (See video at

website: http://polymers.

msel.nist.gov/research

area/multiphase/projectdetail.cfm?P2D=56.). At

the end of this period the

specimen fails in a brittle

manner away from the

observation region. This video indicates that the nucleation of the critical flaw that induces brittle composite

failure may be time dependent and controlled by the

viscoelastic matrix and the mode of interphase failure that

accompanies fiber fracture.

“...understanding how to manage the dissipation of

energy in composite structures during crash conditions

has become critical problem. The goal is to meet or exceed the standard that has been set by steel.”

Nancy L. Johnson

Director for Focal Project 3–ACC

Vehicle Analysis and Dynamics Lab–GM

“Although DOE and others are doing crash energy management modeling, computational models that accurately predict energy dissipation during crash scenarios

are still lacking.”

Raymond G. Boeman, Ph.D.

Automotive Composites Specialists

Oak Ridge National Laboratory

four fiber diameters in the array, the fiber breaks in adjacent fibers are not aligned vertically as predicted by

theory. Computational predictions indicate that the stress

overload in adjacent fibers is smaller for non-aligned

breaks. Hence, the composite toughness is predicted to

be higher. The mechanism(s) that generates the nonalignment of fiber breaks, however, is not well understood.

The change in contrast between Figure 1 and Figure 2

visually represents the stress relaxation in the viscoelastic

matrix after a period of 24 h. The persistent hue after 24 h

between fiber breaks in adjacent fibers is permanent deforFigure 3. Fiber break patterns and matrix deformation in

E-glass/DGEBA/m-PDA 2-D multi-fiber array (unstressed and fibers touching).

G.A. Holmes, W.G. McDonough, C.C. Han (Polymers Division, NIST)

See website: http://polymers.msel.nist.gov/researcharea/multiphase/projectdetail.cfm?PID=56
Technical Highlights

14

Over 100,000 bone grafts are performed each year in the

United States, but the amount of available autologous

bone is limited and available material is difficult to shape.

Thus, the development of a synthetic, moldable bone graft

material is a primary goal of the tissue engineering industry. A self-setting calcium phosphate cement (CPC) that

can be sculpted to fit the contours of a wound and consists of dicalcium phosphate and tetracalcium phosphate

was designed by co-workers from the American Dental

Association Health Foundation at NIST. We sought to

improve this cement by making it macroporous and

osteoinductive through inclusion of polymer microspheres

and a bone growth factor, respectively.

We have assessed the biocompatibility of the

macroporous composite bone graft (CPC polymer) consisting of self-setting calcium phosphate cement and biodegradable polymer microspheres (175 μm–355 μm diameter)

using cell culture techniques. CPC powder was mixed with

polymer microspheres and water to yield a workable paste.

The cement then hardens into a matrix of hydroxyapatite

microcrystals containing polymer microspheres. The rationale for this design is that the microspheres will stabilize

Biocompatibility of a Moldable,

Resorbable, Composite Bone Graft

The blessing of living longer is accompanied by the burden of aging. There is an overall risk of fractures of the hip,

spine and distal forearm that will afflict 40 percent of women and 13 percent of men 50 years of age and older. Restoring form and function to bone defects in an elderly, osteoporotic population of more than 52 million Americans, over

the age of 65 by the year 2020, will be a daunting challenge. To meet this challenge, scientists from the Polymers Division and the American Dental Association Health Foundation have used polymers, calcium phosphates and growth

factors to develop a biodegradable composite bone graft for bone regeneration. The composite bone graft was found to

be biocompatible and to release at a controlled rate a growth factor that stimulates bone regeneration.

initially the graft, but then can gradually degrade, functioning as a ‘polymer porogen’ to leave behind

macropores for colonization by osteoblasts. The CPC

matrix then potentially could be resorbed and replaced

with new bone.

In the present work, osteoblast-like cells (MC3T3-E1 cells)

were seeded onto control CPC (CPC cement only, without

polymer microspheres) or CPC-polymer specimens and

evaluated with fluorescence microscopy (live-dead stain),

scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM) and the Wst-1 assay (a

colorimetric, enzymatic assay for mitochondrial dehydrogenase activity). Examples of data are shown in Figures 1–

3. Cells were able to adhere, attain a normal morphology,

proliferate, and remain viable when cultured on the new

composite graft (CPC-polymer) or on the control graft

(CPC alone). These results suggest that our new cement

consisting of CPC and polymer microspheres is

biocompatible. This is first time that a ‘polymer-in-mineral’

(polymer microspheres dispersed in a CPC matrix) cement

has been formulated that is moldable, resorbable and that

can form macropores after the cement has set.

Figure 1 (left): SEM of the interior of CPC without polymer microspheres (left half) or with polymer microspheres (right

half). The specimens were aged for 3 months in cell media to allow complete degradation of the polymer microspheres.

Macropores (175 μm–355 μm in diameter) formed by the degradation of the polymer microspheres are visible in the

right half panel. The inset is a larger view of the entire CPC-polymer specimen (6 mm in diameter by 4.5 mm in height).

Figure 2 (right): SEM of cells cultured overnight on a CPC specimen which shows that cells can adhere and maintain a

normal morphology when cultured on the cement. “Cell” indicates the cells and “CPC” indicates the cement.
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15

Additionally, we have improved the CPC by providing

controlled release of an osteoinductive protein,

transforming growth factor-β1 (TGF-β1). Initial release

studies using a model protein (fluorescein-labeled Protein

A) showed that protein release kinetics could be

modulated by adjusting the amount of a porogen

(mannitol) included in the CPC (Figure 4). More recent

studies have used TGF-β1 (Figure 5) in a composite of

CPC with salicylic acid as the porogen. In addition,

release kinetics have been studied in CPC-containing

biodegradable polymers as porogens, similar to the CPCpolymer described above. These studies have shown that

release kinetics can be governed not only by the volume

fraction of the porogen, but also by the composition of

the porogen included in the cement (mannitol, salicylic

acid or degradable polymer). These data have garnered

interest from several biotechnology companies that focus

on the development of bone grafts.

The “polymer-in-mineral formulation is what separates”

this cement “from the prior mineral-in-polymer formulations”—Reviewer for Journal of Orthopaedic

Research

Figure 3: Wst-1 assay for cells cultured 2 weeks on

CPC and CPC-polymer specimens. The enzyme reaction

was quantitated by measuring the absorbance (450 nm) of

the reaction wells and shows that the amount of dehydrogenase activity (which is proportional to cell number)

present on CPC specimens is statistically the same as

that found on specimens of CPC and polymer

microspheres (CPC-polymer).

Figure 4: Release of fluorescein-labeled Protein A into

phosphate-buffered saline at 37 o C from CPC/mannitol

composite containing varying volume % of mannitol.

Figure 5: Release of TGF-β1 into phosphate-buffered

saline at 37 o C from CPC/salicylic acid composite.

F.W. Wang, C.G. Simon, Jr., C.A. Khatri (Polymers Division, NIST)

Wang F.W., Khatri C.A., Hsii J.F., Hirayama S., Takagi S. (2001) Polymer-filled calcium phosphate cement: mechanical properties and protein release. J. Dent. Res.

80:591.

Simon, Jr., C.G., Khatri C.A., Wight S.A., Wang F.W. (2001) Preliminary Report on

the Biocompatibility of a Moldable, Resorbable, Composite Bone Graft Consisting

of Calcium Phosphate Cement and Poly(lactide-co-glycolide) Microspheres.

J. Orthoped. Res., submitted.
Technical Highlights

16

Over the past 50 years, there has been sustained interest

in the understanding and control of instabilities that occur

upon pressure driven extrusion of molten polymers. These

instabilities limit the manufacturing rate and the materials

selection in continuous forming operations, such as sheet

extrusion. Processors are forced to sacrifice final mechanical properties to achieve greater processability. From the

scientific point of view, the understanding of these instabilities is challenging; despite much progress, fundamental

issues remain unresolved. An understanding of the cause

of sharkskin would enable a more rational design of materials in order to eliminate it.

In this work we focus on the sharkskin instability. The

driving force behind the attempts to understand sharkskin

is that linear polyethylene of narrow molecular mass distribution particularly is susceptible to this instability. As this

instability occurs at relatively low-extrusion rates, it is

troublesome. The subject has received renewed attention

because newer metallocene-based polyethylene offer

advantages in mechanical properties, but often suffer from

this extrusion instability. There have been numerous suggestions for the mechanism of sharkskin and for an elucidation of the conditions that produce it.

In 1977 it was suggested that sharkskin is caused by a

tearing of the polymer at the exit lip due to the high extensional flow forces generated at this point. Under these

conditions, the extensional stress exceeds the cohesive

strength of the molten polymer. In an alternative picture,

the material undergoes cavitation just inside the tube,

causing sharkskin. Others have suggested that sharkskin

is due to an unstable flow boundary condition that oscillates between stick and slip. These models (and several

others not mentioned for reasons of space) all make specific predictions about the nature of the polymer flow field.

Of particular relevance is the question of whether or not

the polymer sticks to the wall during sharkskin, or if it

slips.

The aim of these experiments is to distinguish among the

various possibilities described above. Many of these

models can be tested through a combination of microvelocimetry, optical imaging, and surface modification

through fluoropolymer additives. We further conduct

experiments under conditions of maximum industrial

The Mechanism of Sharkskin

The rate limiting step in the manufacture of several important classes of polymeric materials is an extrusion instability

known as “sharkskin” in which the manufactured plastic has a rough surface containing a repeated pattern of ridges.

This roughness causes a loss of clarity and a loss of ability to control final part size. Studied since the second world

war, the cause of sharkskin remains an unsolved problem. Here we use the NIST Extrusion Visualization Facility to

capture the step-by-step kinetics of this extrusion instability. We are thus able to determine which of the proposed

causes of sharkskin is actually responsible.

Figure 1: As the extrusion rate increases, the final product becomes progressively distorted. (A) through (D) are

known as sharkskin and (E) is known as gross melt

fracture.

In the case of extrusion through a capillary die, at sufficiently low extrusion rates, the polymer’s surface is

smooth as it exits from the die. At progressively higher

extrusion rates, a series of flow instabilities occurs. The

first instability that may occur is known as sharkskin or

sharkskin melt fracture and is characterized by surface

roughness. At higher extrusion rates, one observes an

oscillating stick-slip transition, followed at higher rates by

gross melt fracture in which the polymer is extruded in an

extremely irregular fashion. The occurrence of the instabilities is dependent on many factors, including polymer

chemistry, molecular architecture, molecular mass and

distribution and polymer/wall surface interactions.

Figure 2: High-speed video microscopy reveals that the

polyethylene splits into a core region and a surface region as it exits the capillary tube.
 Technical Highlights 

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relevance by use of polyethylene processed by twin-screw

extrusion.

In one set of experiments, we use high-speed video microscopy to monitor the kinetics of the flow discontinuity outside the die (Figure 2). We found that the polyethylene

material splits cohesively into a slow moving surface region

and a fast moving core region, the latter contains the majority of the material. The surface region bulges upwards and

then breaks off from the exit lip.

When we monitor the flow kinetics inside the capillary

tube, we find that the flow kinetics is smooth, even well

above the onset of the sharkskin instability. Unsteady flow

conditions are observed only under shear stresses close to

that of gross melt fracture. Significantly, we find that

sharkskin can occur under conditions of both stick and

slip. This observation helps to reconcile many years of

debate on the question of whether stick or slip boundary

conditions prevail during sharkskin. We find that either

one is possible, as long as the critical stress at the exit is

exceeded!

A crucial test of exit stretching as a cause of sharkskin was

done by comparing the onset of sharkskin in resins with

and without a fluoropolymer additive. We found that the

extensional deformation rate was comparable at the onset;

the first parameter that has shown to correlate with the

onset of sharkskin.

Now that we understand the mechanistic aspects of the

instability, we can concentrate on material related questions. For example, why does long-chain branching and

molecular mass distribution affect this instability, and why

related materials (such as polypropylene) suffer much less

from this instability?

Figure 3: High-speed images of the exit region as the

extrusion rate increases. Figures (B–E) correspond to

 (A–D) in the first image sequence (Figure 1).

K.B. Migler

Migler, K.B., Lavallée, C., Dillon, M.P., Woods. S.S., Gettinger, C.L., Visualizing the

elimination of sharkskin through fluoropolymer additives: Coating and

polymer-polymer slippage, Journal of Rheology 45, 565-581 (2001).

Figure 4: Flow velocimetry inside the tube (x<0) and

outside it (x>0) is shown for the case of the bare surface

(upper plot) and in the case of a fluoropolymer additive

(lower).

“Our experiments with NIST using their Extrusion

Visualization Facility have resulted in breakthroughs

in our abilities to conceptualize and understand how

fluoropolymers reduce sharkskin. These measurement

tools strongly impact our efforts in new product

development.”

Claude Lavallée

3M Canada Company

Contact Information:

19

Combinatorial Methods

The Combinatorial Methods Program develops new measurement techniques and experimental strategies needed

for rapid acquisition and analysis of physical and chemical

data of materials by industrial and research communities.

A multi-disciplinary team from the NIST laboratories participates to address key mission driven objectives in this

new field, including needed measurement infrastructure,

expanded capability, standards and evaluated data.

Measurement tools and techniques are developed to

prepare and characterize materials over a controlled range

of physical and chemical properties on a miniaturized scale

with high degree of automation and parallelization. Combinatorial approaches are used to validate measurement

methods and predictive models when applied to small

sample sizes. All aspects of the combinatorial process

from sample “library” design and library preparation to

high-throughput assay and analysis are integrated

through the combinatorial informatics cycle for iterative

refinement of measurements. The applicability of combinatorial methods to new materials and research problems is

demonstrated to provide scientific credibility for this new

R&D paradigm. One anticipated measure of the success of

the program would be more efficient output of traditional

NIST products of Standard Reference Materials and evaluated data.

Through a set of cross-NIST collaborations in current

research areas, we are working to establish the infrastructure that will serve as a basis for a broader effort in combinatorial research. A Combinatorial Methods Working

Group (CMWG) actively discusses technical progress

within NIST on combinatorial methods through regular

meetings. The technical areas and activities of the CMWG

are available in a brochure “Combinatorial Methods at

NIST” (NISTIR 6730). Within MSEL, novel methods for

combinatorial library preparation of polymer coatings have

been designed to encompass variations of diverse physical and chemical properties, such as composition, coating

thickness, processing temperature, surface texture and

patterning. Vast amounts of data are generated in a few

hours that promote our understanding of how these variables affect material properties, such as coatings

wettability or phase miscibility. Additional focus areas for

both organic and inorganic materials include multiphase

materials, electronic materials, magnetic materials,

biomaterials assay, and materials structure and properties

characterization. State-of-the-art on-line data analysis

tools, process control methodology, and data archival

methods are being developed as part of the program.

In order to promote communication and technology transfer with a wide range of industrial partners, an industrynational laboratories-university combinatorial consortium,

the NIST Combinatorial Methods Center (NCMC) is being

organized by MSEL. The NCMC will facilitate direct interactions on combinatorial measurement problems of broad

industrial interest and efficient transfer of the methods

developed to U.S. industry.

Alamgir Karim
Combinatorial Methods

Contributors

and

Collaborators:

20

High-Throughput

Measurements of

Crystallization and

Nucleation in Polyolefins

A. Karim, K.L. Beers, A.P. Smith, M. Walker, and J.F. Douglas (Polymers Division,

NIST)

Figure 1. The measured rates, G, as a function of crystallization temperature, T. (Curve is data from J. Boon, et al., J.

Polym. Sci., Pt. A-2, 1968, 6, 1971.)

The ability to direct or suppress order in polymeric thin

films has many practical implications for industrial materials.

In particular, the degree of crystallinity in semi-crystalline

polymer films can be affected dramatically by a host of

processing conditions such as solvents, thermal history,

additives, etc. Developing a high-throughput method of

screening these effects has the potential to quickly optimize

the processing of materials, as well as probe many of the

outstanding theoretical issues regarding the nature of polymer crystallization.

The gradient film technology developed at NIST presented

itself as a promising solution. Concerns regarding the continuity of the films, however, prompted a general “proof of

principle” test application. Hence, isotactic polystyrene,

iPS, extensively a slowly crystallizing polymer, was investigated. In one continuous film, the crystal growth rates, G,

The morphology and degree of crystallinity in semicrystalline thin films has a dramatic impact on their

performance factors such as stability, optical properties

and conductivity. Since the parameter space governing

this problem is large and the theoretical understanding

of thin-film crystallization is limited, we study a model

polymer (isotactic polystyrene) as well as isotactic

polypropylene using combinatorial, high-throughput

methods. The effects of film thickness, under-cooling

temperature and nucleating agents are currently under

investigation. The morphology and kinetics of spherulitic structure growth is investigated combinatorially.

were measured as a function of temperature and film thickness, yielding data from one experiment, which previously

would have required the preparation of dozens of discrete

films.

The films were prepared using the gradient flow coating

technique. Crystal growth was observed using a Nikon

Optiphot optical microscope and crystal structure analysis

was carried out using a Nanoscope Dimension Series

atomic force microscope.

Because iPS crystallizes comparatively slowly, it is possible to study the kinetics over a wide range of temperatures, from just below Tm to close to the glass transition

temperature, Tg. In this case, a span of 70 °C was typically

covered (from 130 °C to 200 °C), a range in which it has

been shown that the rate passes through a maximum between 175 °C and 180 °C. Good agreement was found in

the high-throughput experiment on continuous films for

these rates as a function of temperature (Figure 1). More

recently, the effects of film thickness, h, on the rate of

crystallization in iPS thin films were studied; G decreased

with h below 50 nm. We observed a similar trend in the

continuous films.

Under similar experimental conditions, isotactic polypropylene yields faster, more difficult to measure rates of

crystallization; however, the dependence of morphology

and degree of crystallization on common nucleating

agents can be observed in conjunction with other parameters such as h and T. Films containing small amounts of

nucleating agents, such as 4-biphenyl carboxylic acid, and

ranging in thickness from 50 nm to 150 nm are currently

under investigation in the temperature range from 100 °C

to 150 °C .

These results validate the high throughput/combinatorial

approach to investigating polymer crystallization in thin

films, accelerating the pace of experimentation by increasing the parameter space available for sampling. Furthermore, the dependence of G on h and T was explored in two

dimensions to a degree previously considered unfeasible.

Kathryn L. Beers, Alamgir Karim
 Combinatorial Methods 

Contributors

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21

Combinatorial Mapping of

Polymer Film Wettability

Karen M. Ashley, Amit Sehgal,

D. Raghavan, Alamgir Karim

A. Sehgal, J.F. Douglas, A. Karim (Polymers Division, NIST)

K. Ashley, D. Raghavan (Howard University, Washington DC)

The ubiquitous use of polymer films in protective coatings,

paints, inks, and adhesive layers relies on the ability of the

polymer to spread effectively on or “wet” the underlying

substrate. The advent of conducting polymers, molecular

electronics, and polymers in the photonics and electronics

industry, and the concurrent drive to smaller devices have

further extended use of ultrathin films, where film stability is

critical to the performance of the device. Conversely, a

fundamental understanding of stochastic processes such as

dewetting generates nano- to micro-scale surface structures

that may be utilized for optical and biological applications.

Interfacial interaction of the polymer with the underlying

substrate is one of the key parameters that influence the

stability of thin polymer films. An approach to preparing

gradient energy surfaces is developed, by immersing an

Si-H passivated silicon wafer in Piranha solution (H2

SO4/

H2

O2/H2O) at a controlled rate, producing a monotonic

variation of solvent (water and di-iodomethane) contact

angles across the surface. As expected, regions of the substrate that had longer exposure to the Piranha solution and

higher concentrations of H2SO4 in the Piranha solution

were more hydrophilic (lower water contact angles).

Thickness gradients of low molecular mass polystyrene

were prepared on the chemical gradient wafers orthogonal

to the surface energy dispersion using a velocity-gradient

knife-edge coating apparatus. Film thickness (h) of the

coating was measured by automated spectroscopic spot

interferometry producing contour maps of film thickness.

Thus, a typical combinatorial library sample film is prepared

to map efficaciously thin-film wettability.

Combinatorial sample libraries were screened by reflection

optical microscopy for dewetting behavior. Composite images were obtained as shown in the figure, characterized by

substrate water contact angle and initial film thickness of

polystyrene given in parenthesis. Dewetting occurred by

the growth of small circular holes whose rims impinge to

form small polygons within 2 h of annealing time at 100 °C.

We performed a quantitative analysis of the dewet structures by dividing the combinatorial library into a virtual

The stability of thin polymer films is of primary significance not only in their extensive application as photoresists, paints and adhesives, but increasingly in electronic

and photonic devices and in the biomedical industry.

Knowledge of failure mechanisms of thin polymer film

breakup, in the context of variables such as substrate

surface energy, thickness and temperature, is crucial for

their applicability. We use combinatorial methods to

explore rapidly parameter space to map regions of film

wettability and simultaneously further fundamental understanding of thin-film rupture.

array of individual cells with varying contact angles and film

thickness values. By using an automated batch program,

the images were thresholded and the number of polygons

determined.

The local polygon density (Np per unit area in an image

box) of dewetted polymer was found to obey a power-law

relationship with film thickness (Np~h-4.3) that is in agreement with reported literature value for ultra-thin films on

strongly hydrophilic surfaces (spinodal-dewetting regime).

After validating the high-throughput screening method by

comparison to previous studies of thickness effect on dewetting, a novel power-law relationship between the water

contact angle of the substrate (θwater) and the number of

polygons of dewetted polystyrene film at constant thickness was also established to be (Np

~θwater

-3.6). These studies

suggest that the late-stage dewet polymer pattern dimensions are critically sensitive to surface hydrophilicity and

film thickness.

A more versatile and critical approach to preparing gradient

energy surfaces is being developed by depositing chlorosilane self-assembled monolayers on silicon surface followed by exposure to UV radiation. Combinatorial libraries

of a biocompatible polymer poly(DL-lactic acid), and phase

separated blends with poly(ε-caprolactone) for use as patterned templates for cell proliferation studies are being

investigated on these surfaces.
Combinatorial Methods

Contributors

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Collaborators:

22

Anisotropic Adhesion

Between Polymers,

Metals, Ceramics and

Biomaterials

A.J. Crosby, A. Karim, E.J. Amis (Polymers Division, NIST)

Figure 1: PDMS microlens used for combinatorial adhesion test.

We have developed a combinatorial technique to investigate adhesive interactions between a polymer and another

polymer, ceramic or metal. The primary goal in the development of this technique was to design a high-throughput,

parallel processing adhesion test that allows the adhesive

strength dependence on multivariable parameters and environmental conditions to be determined.

This combinatorial methodology for measuring polymer

adhesion is largely built upon the theory of Johnson,

Kendall, and Roberts (JKR), which facilitates the measurement of adhesive forces between two contacting surfaces.

In the classical use of this theory, a hemispherical lens of

one material is brought into contact with a complementary

substrate, and subsequently separated. In our work, rather

than using a single hemispherical lens, we use an array of

microlenses. During this process, the contact area and

displacement of each microlens is recorded through the use

of an image acquisition system integrated with an optical

microscope. With these parameters, the JKR theory can

then be used to quantify the adhesion energy between the

two contacting materials. Along each axis of the array, a

gradient in different environmental parameters or material

properties can be placed. Examples of such gradient properties are: surface energy, temperature, thickness, crosslink

density, blend composition and strain. If two orthogonal

Alfred Crosby, Alamgir Karim, Eric J. Amis

Polymer adhesion is important to numerous technologies

including electronic packaging, coatings and paints,

biomedical implants, and pressure-sensitive adhesives.

Current methods for characterizing adhesion are either

inefficient or ineffective. Here we develop and implement a

combinatorial method to qualitatively and quantitatively

map polymer interfaces to assess the dependence of anisotropic polymer adhesion on multivariable parameters. This

technique allows us to not only identify optimal environments for the adhesion of given polymer interfaces, but

also facilitates the fundamental investigation of how

molecular structure and chemistry define adhesion.

gradients are placed on the array, then each microlens contact point will yield a measurement of adhesion for a unique

combination of parameters. With our current microlens

libraries, we are capable of measuring 1,600 different points

of adhesion within a single test.

To demonstrate this methodology, we investigated the

effect of thickness and temperature on the self-adhesion of

polystyrene (PS). In this test, a microlens array was made

from poly(dimethylsiloxane) (PDMS). Onto this PDMS

array, we floated a thin layer of PS containing a thickness

gradient. The complementary substrate for this test was a

PS-coated silicon wafer with an applied temperature gradient. During contact, the PS molecules diffuse across the

interface, entangle, and strengthen the interface, thus causing the PS coating of the PDMS microlenses to delaminate

within the contact regions. This “welding” of the contact

areas occurs above a critical temperature and below a critical thickness over the time scale of our test. This measurement is useful for the microelectronics industry where adhesion of thin polymer layers determine the integrity of

electronic packaging, but the general technique will have

impact on the numerous industries where adhesion plays a

dominant role.

Figure 2. Temperature and thickness dependence on

critical PS welding temperature.
 Combinatorial Methods 

Contributors

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Collaborators:

23

Cellular organization in tissue is guided by or even altered

by the extra-cellular matrix, a heterogeneous complex environment, comprising of spatially distributed structural and

functional components. We utilize blend phase separation

to create novel multicomponent biomimetic

materials, where the

intrinsic heterogeneity

is exploited to build in

structure and function.

We are also motivated

by the awareness that

the biomedical industry

is constrained to the

use of relatively few

materials approved by

regulatory bodies,

often compromising on

the mechanical or the

functional demands of

the medical device. The

use of blends of approved materials,

where one component

provides bioreceptive

functionality while the

other provides the

structural reinforcement, greatly enhances

the range of biocompatible materials available to

the industry to improve ultimately the performance of medical devices. Further, we harness the physics of blend phase

separation in confining geometries of thin films and chemically patterned substrates to create highly structured polymeric templates to guide and test cellular response.

Pattern-directed phase separation of polymer blends was

used to create libraries of spatial distribution of bioreceptivity. The substrates are patterned chemically by soft

Patterned Polymeric

Substrates for Directed

Cell Growth

Amit Sehgal, Alamgir Karim, Eric J. Amis

The new paradigm for clinically relevant biomaterials is

inspired by nature itself. The level of complexity inherent

in the organization of tissue is extended to the design of

biomaterials with a high level of control of surface functionality and topography. We combine the rich microstructure of polymer blends with tools such as surface

patterning to create unique highly structured testsubstrates for cell response. These surfaces have a systematic variation of spatial scales and properties across a

single test-substrate to assay optimal structure for cellular reception in a high-throughput fashion.

lithography to have a range of stripe pattern sizes on

single test substrates. The self-organization of a biodegradable blend of poly(ε-caprolactone) [PCL] and poly(DL lactic acid) [PDLA] on the chemical stripe patterns then

generates a model blend substrate to correlate cell response to the scales of spatial distribution and size of the

blend components. Here, the PCL comprises the semicrystalline structural component while the PDLA is the

more bioreceptive hydrophilic component.

Evaluation of response of osteoblast-like mouse calvarial

(MC3T3) cells on the phase separated patterns shows

anisotropic cell focal adhesion specifically to the PDLA

rich phase where the underlying material anisotropy

guides the preferential cell orientation (Day 1). This is

followed by anisotropic liquid like cell spreading (Day 3)

where the cell pseudopodia develop preferentially along

the PDLA rich ridges. This behavior is also found in the

non-patterned isotropic regions but the cell spreading is

isotropic. It was also found that the periodicity of the focal

adhesion is regulated by the underlying pattern frequency.

The systematic variation of surface structure enables us to

interrogate the effect on possible cytoskeletal rearrangement and regulation of specific pathways and ultimately

guide cell function.

Figure 1. Anisotropic cell adhesion on PCL/PDLA patterns.

A. Sehgal, A. Karim, J.F. Douglas, E.J. Amis, C.G. Simon, Jr. (Polymers Division,

NIST)

Figure 2. Pattern directed cell spreading. (Day 3)
Combinatorial Methods

Contributors

and

Collaborators:

24

LCM was designed to target specific cell populations (cancerous cells) from tissue sections to study genetic mutations without “contamination” from surrounding (healthy)

tissue. Resuspension in aqueous media however limits

analysis of the extracted DNA, RNA and proteins from the

captured cells due to high levels of dilution. This motivates

encapsulation of captured cells in tailor-made microwells

with femtoliter volumes preserving high macromolecular

concentrations with increased sensitivity enabling new

detection and in-situ analysis methods.

Our method of laser-induced fabrication simply employs the

use of an absorbing dye in a thin polymer films creating

thermally induced microchannels and microwells. Given the

Microwell Arrays for Laser

Capture Microdissection

(LCM)

Giovanna Cantoni, Amit Sehgal,

Robert F. Bonner, Alamgir Karim

LCM was developed as a prototype research tool at the

National Institute of Child Health and Development

(NICHD) and the National Cancer Institute(NCI) of NIH.

It refers to a microscope equipped with a laser to target

and capture single cancerous cells from frozen tissue

sections on a fusible polymer film. We have developed

methods to augment the LCM by enabling encapsulation

of the captured cells in microwells of femtoliter (10-15 L)

volumes with minimal dilution enabling in-situ single

cell analysis. We demonstrate the use of combinatorial

methods for mapping parameter space for laser-induced

microfabrication of microwell arrays.

range of variables (laser power, pulse duration, spot size,

film thickness, dye concentration, thermal conductivity of

the film, substrate, etc.) we resort to combinatorial methods

for high-throughput mapping of microfabrication parameters. An example of high-throughput characterization (Figure 1) of a grid of programmed contiguous atomic force

microscopy scans of a microwell array maps the effect of

laser power and pulse duration on critical microwell dimensions while other parameters (dye concentration, thickness)

on a single surface are held constant. The wells form ideal

receptacles for captured dried tissue (Figure 2).

The thermally induced fabrication process is extremely

sensitive to the thickness of the insulating polymer film or

proximity to the thermally conductive glass substrates.

Section profiles confirm the expected increase in depth with

pulse duration that becomes constant as the well nears the

polymer glass interface. This suggests an ablative process

that ceases as thermal conduction to the glass lowers the

peak surface temperature of the depleting polymer layer. An

opposing effect was discovered at lower laser powers,

suggesting a non-ablative mechanism whereby a locally

fused film (lower peak temperatures) buckles to form a meniscus due to the differential in surface tension of the fluid

and the surroundings. This process allows for a novel

method for structuring thin films without chemical modification (oxidation or etching).

A. Sehgal, A. Karim (Polymers Division, NIST)

G. Cantoni, R.F. Bonner (LIMB/NICHD, NIH)
 Combinatorial Methods 

Contributors

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Collaborators:

25

Newell R. Washburn and Alamgir Karim

A method for preparing polymeric scaffolds for tissue

engineering without the use of organic solvents has

been developed. Borrowing techniques from polymer

processing, a biocompatible polymer such as

poly(ε-caprolactone) or poly(ethyl methacrylate) is

blended with a biocompatible, water-soluble polymer

such as poly(ethylene oxide). After annealing the blend,

the water-soluble component is dissolved yielding a

porous material. The pore connectivity and characteristic

length scale may be controlled by tuning the blend composition and annealing time and temperature. In this

work we have focused on blends that have a continuous

network of pores and length scales ranging from 10 μm to

100 μm.

We are using these scaffolds to investigate several fundamental issues in tissue engineering such as the influence of scaffold composition, dimensions, and structural

anisotropy on cell proliferation and matrix deposition.

Concomitantly, we are also developing new techniques

for characterizing both the materials and the tissue development in them.

Figure 1 shows images of poly(ethyl methacrylate) scaffolds that were prepared with a continuous network of

pores having a characteristic dimension in excess of 100

micrometers. The scaffold was seeded with primary chick

osteoblasts and cultured in a perfusion bioreactor for 6

weeks. Afterwards, the cell-scaffold constructs were

fixed and stained for collagen using Sirus Red and mineral using von Kossa then sectioned using standard

histological techniques. The stained areas in the porous

structure are areas where significant matrix deposition

has occurred.

In collaboration with researchers at the Armed Forces

Institute of Pathology and National Institutes of Health,

we have been developing the use of magnetic resonance

imaging for studying tissue development in situ. In Figure 2 are shown the T1 and magnetization transfer (MT)

scans for these scaffolds after 5 weeks of culture. The

Tissue Development in

Co-extruded Polymer

Scaffolds

A method for preparing tissue engineering scaffolds using

techniques borrowed from polymer processing has been

developed. Characterization of tissue development in

these scaffolds is under way in collaboration with researchers at the Armed Forces Institute of Pathology

(AFIP) and the National Institutes of Health (NIH). Primary chick osteoblasts were cultured on the scaffolds in a

perfusion bioreactor and matrix deposition was monitored using magnetic resonance imaging and histology.

image shown is a cross-section of a 2-mm-thick disk and the

spatial resolution of the scans is 100 μm. The T1 scan has

black regions where water has been excluded from regions

of mineral deposition and the MT scan has bright regions

where collagen deposition has occurred. The contrast in the

scans is consistent with the observation that the cell coverage is likely inhomogeneous, leading to inhomogeneous

matrix deposition.

N.R. Washburn, A. Karim, J.P. Dunkers, E.J. Amis (Polymers Division, NIST)

K. Potter (AFIP), F. Horkay (NICHD, NIH)

Figure 1. Histology sections of scaffolds that were stained

for mineral (left) and collagen (right). The field of view is

100 μm.

Figure 2. Magnetic resonance imaging scans for mineral

(left) and collagen (right). The image is a cut through the

scaffold, which is 2 cm in diameter.

Current work is focused on calibrating the magnetic resonance signal for performing quantitative assessment of

tissue development and addressing the fundamental issues

related to tissue engineering discussed above. We also are

attempting to develop functional imaging techniques that

yield more information about metabolic activity of the cells.
26

Interface of Materials with Biology

New materials and devices are changing radically the medical treatment of injury and disease, yet because of the rapid

growth of this segment of the materials industry, an adequate measurement infrastructure does not exist. The

program on the Interface of Materials with Biology

develops measurement methods, standards, and fundamental scientific understanding at the interface between materials science and biological science. Within the health care

industry we focus on dental and medical sectors that apply

synthetic materials for replacement, restoration, and regeneration of damaged or diseased tissue.

Four major activities constitute this program:

• The dental industry is composed largely of small manufacturers with very little R&D capability. The dental

materials projects, carried out in close collaboration with

the American Dental Association fill that need by developing improved materials and techniques, patenting

these inventions, licensing to these small companies,

and most importantly, providing technical assistance to

these licensees for producing and improving their products. This has provided U.S. companies with products

that successfully compete on a worldwide market. Our

research focuses on improved understanding of the

synergistic interaction of the phases of polymer-based

composites and the mechanisms of adhesion to dentin

and enamel. This approach will ultimately lead to materials with improved durability, toughness and adhesion to

contiguous tooth structure.

• The tissue engineering industry shows the potential for

explosive growth in the coming years as biomedical

research is moving from academic science to industrial

application at an increasing rate. Our work seeks to

bridge the gap between knowledge generation by cell

biologists and product development in industry. In

collaboration with the NIST Biotechnology Division we

are developing a set of measurement methodologies and

reference materials to use in assessing interactions in

complex systems of living cells with synthetic materials.

The expected outcomes of this work include reference

substrates that induce gene expression associated with

specific stages in cellular activity, and engineered DNA

vectors that signal fluorescently these responses in

adherent cells.

• Regenerating form and function to bone defects in an

elderly, osteoporotic population of Americans will

be a daunting challenge. To meet this challenge, we are

developing metrology methods to characterize the

biocompatibility of bone grafts for bone regeneration.

Quantitative methods being developed include bioassays for the adhesion, viability, proliferation, and alkaline phosphatase activity of bone cells, as well as confocal microscopy and optical coherence tomography for

measuring the growth of bone cells into bone grafts. A

combinatorial approach is being used to rapidly identify

compositions and surface features of bone grafts that

provide desirable properties such as biocompatibility

and mechanical durability.

• The NIST Center for Neutron Research and the NIST

Biotechnology Division are engaged in the study of

biomimetic films that serve as models of cell membranes

and which are of fundamental importance in understanding such key biological processes as phospholipid selfassembly, molecular recognition and cell-protein interactions. Recent improvements in neutron reflectometry at

the NCNR, coupled with advances in biomimetic film

fabrication at metallic interfaces pioneered in the Biotechnology Division, afford enhanced sensitivity for

probing membranes and membrane-protein complexes.

New phase sensitive measurement techniques and

model-independent data analysis methods have demonstrated the feasibility of obtaining reliable depth profiles

of membrane structures in contact with biologically

relevant aqueous environments, achieving

subnanometer spatial resolutions.

Fundamental to all the work in this program is the recognition that surfaces and interfaces play a critical role in biological systems and, in particular, in the interactions of

synthetic or designed materials with biological systems

and function. By providing the unique expertise in the

NIST Materials Science and Engineering Laboratory to

characterization of surfaces and interactions at interfaces in

biomaterials we will accelerate the introduction of improved

materials and help provide the means to assure quality

control that is critical to this industry.

Contact Information: Eric J. Amis
 Interface of Materials With Biology 

Contributors

and

Collaborators:

27

It is well known that the primary (amino acid sequence),

secondary (beta sheet, alpha helix, etc.) and tertiary

(folded) structures of a protein are crucial for enzymatic

activity. However, dynamics ranging from the picosecond

thermal fluctuations to the millisecond (and slower) conformational changes are also requisite for biological function. At the high frequency end, neutron scattering quantifies the local thermal fluctuations in terms of a mean

square atomic displacement <u2>. Several studies have

shown that in hydrated proteins there is a dynamic transition, Td

, near 180 K to 220 K (reportedly the Tg of supercooled water) where a sudden change of <u2

> occurs and

above which the thermal fluctuations become strongly

anharmonic. It is also known that Td coincides with the

onset of enzymatic activity. These fluctuations are

thought to enable the large-scale conformational changes

that accompany biological function.

The Dynamic Effects of

Protein Stabilization in

Glass Forming Liquids

Christopher L. Soles, Amos M. Tsai

The stability of protein and enzyme molecules is of great

interest to the pharmaceutical industry. However, the

main attributes constituting a stable environment are not

yet fully identified. Excesses in temperature and/or dehydration irreversibly damage most enzymes, proteins, and

cellular structures. While a few viscous alcohol or sugar

co-solvents are known to provide this stability, the responsible mechanisms are poorly understood. Inelastic

neutron and low-frequency Raman scattering are used to

probe the dynamic effects of these viscous sugars/

alcohols to help resolve the mechanisms of protein

stabilization.

peratures commensurate with its own glass transition. It is

believed generally that the reduced mobility imparted by

the viscous glycerol, a widely used cryo-protectant in

biological freeze-drying processes, is vital for stability.

This leads to the notion that a high Td

 is desirable in a

protein stabilization scheme. However, there is more to

protein stabilization than glass formation alone. Below Td

glycerol suppresses <u2> the harmonic motions of

lysozyme. This is quantified as a stiffening of the elastic

force constant defined by the thermal evolution (i.e.,

slope) of <u2>; stiffer vibrations increase less dramatically

in amplitude with T. From the previous figure, glycerol

stiffens the force constants of lysozyme by 40 percent.

The effects of this vibrational stiffening are also seen in

the full inelastic neutron scattering spectra. The positions

of the Boson peak of the dry and glycerol-preserved

lysozymein are analyzed in terms of their force constant. In

glycerol the low-frequency mode is shifted to higher energies compared to dry state at the same temperature. This

shift occurs at the same temperatures where the suppression of <u2

> is observed. If this low-frequency vibration

is modeled as a harmonic oscillator (ω2 = k/m), the square

of the peak frequency also stiffens by 40 percent, mirroring the <u2

> data.

The similarities in <u2> and the low-frequency vibrational

spectra suggest that a stabilized protein also has a higher

frequency Boson peak. Recently we corroborated this in

mesophilic and thermophilic (thermally stable) a-amylase;

both a suppressed <u2> and higher frequency Boson

peak are seen in the naturally thermophilic protein. This

provides a powerful tool to assess new preservation

schemes, a process currently done by trial and error. While

<u2> measurements are limited by the availability of neutrons, Boson peak measurements are accessible with conventional low-frequency Raman scattering. This may

provide the pharmaceutical industry a readily available

tool to help evaluate protein stabilization schemes.

J.F. Douglas (Polymers Division, NIST)

R.M. Dimeo, D.A. Neumann, R.L. Cappelletti (Center for Neutron Research, NIST)

G. Caliskan, A. Kisliuk, A.P. Sokolov (University of Akron), M.T. Cicerone

(Brigham Young University), J.J. DePablo (University of Wisconsin)

0.20

0.15

0.10

0.05

0.00

∆ <u2> ( Å2 )

100 150 200 250 300 350

T ( K )

 glycerol

 dry

 wet

kdry = 8.8 N/m

kglycerol = 12.0 N/m

fit range

In proteins stabilized with a viscous alcohol/sugar cosolvent, Td

 typically shifts to higher temperatures. This is

seen in the above figure where the dynamics of dehydrated, hydrated, and glycerol-preserved chicken egg

white lysozyme are compared. Glycerol shifts Td to tem-
Interface of Materials With Biology

Contributors

and

Collaborators:

28

This project is directed toward enhancing our basic understanding of how monomer structure and variations in

comonomer compositions influence the photopolymerization process and the polymeric network structure, both

critical factors that determine the potential properties that

can be achieved with dental polymers and their derived

materials, e.g., composite restoratives. Dental matrix polymers are described often simply as highly cross-linked

networks with little or no characterization done beyond a

measurement of overall vinyl conversion. Although the

results of physical and mechanical property testing also

have been reported widely for dental polymers, these data

would be more useful with knowledge of how monomer

structure and resin composition variations affect the development of cross-linked polymers. Generally this information is difficult to interpret and use as a guide for the

development of improved materials.

In addition, the project is intended to define the

currently unknown co-reactivity of structurally different

co-monomers that are typically used in dental polymers.

For lack of this information, the reactivity and cross-linking potential of dental resins are generally assumed to be

equal. The use of selected model monomers is designed to

demonstrate the influence of specific structural features

on polymer properties and should have significant impact

on the development of improved materials. An examination

of non-methacrylate co-monomers, such as vinyl esters

and vinyl ethers, offers a means to modify network formation and also appears to allow for higher conversion and

improved mechanical properties.

It is known that widely used dental monomers such as the

hydroxylated dimethacrylate Bis-GMA and the urethane

dimethacylate UDMA form strong hydrogen bonds that

are of different types. The effect of hydrogen bonding on

monomer viscosity is well known, but its influence on the

polymerization process and its potential to influence network structure has been overlooked. These aspects are

being examined along with studies of some model hydrogen bonding monomers that directly may provide polyStructure-Property

Relationships in Dental

Polymers

Joseph M. Antonucci

Polymer-based dental materials are used increasingly in

dentistry and allied biomedical fields. As part of a joint

research effort supported by the National Institute of

Dental and Craniofacial Research and also involving

collaboration with the American Dental Association

Health Foundation Paffenbarger Research Center, NIST

is providing the dental industry and the dental profession with a comprehensive knowledge base regarding

polymeric dental materials that will help elucidate the

in-vitro and in-vivo performance of these materials.

mers with improved properties. An interesting example of

the profound effects of hydrogen bonding involved the

comparison of 2-hydroxyethyl methacrylate (HEMA) with

its isomer, ethyl-α-hydroxymethylacrylate (EHMA). The

stronger intramolecular hydrogen bonding of EHMA vs.

HEMA has a significant effect on both monomer and

polymer properties. Also, subtle changes in monomer

structure, for example the substitution of ether linkages

into a predominantly hydrocarbon dimethacrylate, can

produce dramatic differences in polymerization rate and

polymer properties. The systematic introduction of heteroatoms into dimethacrylate monomers currently is being

examined to explain why these differences exist and how

they can be employed to obtain polymers with improved

properties. The use of multi-modal distributions of comonomers with varied chain lengths offers a simple means

to achieve an increased level of vinyl conversion, network

structure variations in the polymer and corresponding

improvements in the physical, chemical and mechanical

properties of dental polymers and derived materials.

A major part of this project is directed at implementing

strategies of maximizing vinyl conversion while minimizing

polymerization shrinkage. Currently we are investigating

high molecular mass urethane and silyl ether derivatives of

Bis-GMA, as well as new types of high molecular mass

diluent monomers, for their efficacy in reducing residual

vinyl unsaturation, polymerization shrinkage and the water

uptake of their polymers. In addition, the use of alternative

initiator systems are under investigation in an effort to

enhance photopolymerization efficiency and alter polymer

network formation. This project is expected to lead to a

better understanding of structure-property relationships

of monomer/resin systems that should translate into polymeric dental materials with improved clinical performance.

The results of these studies should extend well beyond

the dental materials venue to include a significant number

of other applications that rely on the rapid formation of

cross-linked polymeric network having optimal properties

from photopolymerizable monomer systems.

J.M. Antonucci, M.D. Weir, D.W. Liu, C.A. Khatri (Polymers Division, NIST)

S. Dickens (American Dental Association Health Foundation Paffenbarger

Research Center)

J.W. Stansbury (University of Colorado, Boulder)
 Interface of Materials With Biology 

Contributors

and

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29

Over 100,000 operations requiring bone grafts are performed each year in the United States to repair osseous

defects resulting from trauma or disease. Autografts are

widely used by surgeons, but the amount of bone available for autografts is limited and available material is difficult to shape. Thus, the development of synthetic materials for use as bone grafts is a primary objective of the

tissue engineering community. We are using this opportunity to develop metrology to serve this burgeoning industry and to develop a novel composite bone graft.

Our graft consists of a calcium phosphate powder and

small spheres made from a biodegradable polymer that are

mixed with water to form a paste. The paste can be molded

and then sets like cement within 30 min to form a solid

matrix of microcrystalline hydroxyapatite that contains the

polymer spheres. In vivo, the spheres should degrade to

leave behind macropores for colonization by bone tissue.

We are assessing the biocompatibility of the composite

graft and are making the graft osteoinductive by adding

bone growth factors.

By facing challenges that are common to the entire tissue

engineering industry in the context of this real problem, we

can evaluate and improve the existing biocompatibility

metrology. Specifically, we have implemented new techniques for assessing cell morphology, adhesion and proliferation during culture on opaque substrates such as our

bone graft. We are characterizing new fluorescent indicators of cell viability (see figures) and are improving upon

cell preparation techniques for environmental scanning

electron microscopy which allows high-resolution imaging

of hydrated samples. In addition, we are evaluating a new

colorimetric assay for quantifying cell number that is

easier to use and faster than standard assays.

After characterizing our composite bone graft with these

new techniques, we will move to make the best techniques

into standardized assays with the appropriate agencies

(ANSI, ASTM, FDA, ISO). Thus, this project may yield a

new synthetic bone graft material as well as new standards

for use by the tissue engineering industry.

A Moldable, Resorbable,

Macroporous, Composite

Bone Graft Containing

Growth Factor

Carl G. Simon, Jr., Chetan Khatri,

Francis W. Wang

The rapidly expanding tissue engineering industry is in

need of improved measurement technology to aid in the

development of new biomaterials. We are developing this

technology through the design and testing of a novel

composite bone graft. Techniques for assessing cell morphology, adhesion and proliferation on opaque specimens are being evaluated with the aim of proposing the

best assays as new standards to appropriate agencies

(ANSI, ASTM, FDA, ISO). Thus, this project can yield a

new synthetic bone graft as well as new standards for use

by the tissue engineering industry.

F.W. Wang, C.G. Simon, Jr., C.A. Khatri, S.A. Wight, J.F. Hsii (Polymers Division,

NIST)

W. Guthrie (Statistical Engineering Division, NIST)

Shozo Takagi (American Dental Association Health Foundation)

Cells growing on a bone graft specimen which has been

fluorescently double-stained for live (green, top) and dead

cells (red, bottom). Both panels are the same field of view

seen through different filters.
Interface of Materials With Biology

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30

Over the broad range of solution conditions when precipitation occurs spontaneously, amorphous calcium phosphate (ACP) precedes the formation of HAP. ACP has

been shown to have high solubility in aqueous media and

to undergo rapid conversion to HAP, especially at low

pHs. Both of these properties suggest its use as a

bioactive filler in polymeric materials for the preservation

or repair of enamel, dentin, cartilage and bone.

Utilizing conventional dental matrix resins (e.g. 2,2-bis[p-

(2'-hydroxy-3'-methacryloxypropoxy)phenyl] propane (BisGMA), triethylene glycol dimethacrylate (TEGDMA) and

2-hydroxyethyl methacrylate (HEMA)) and ACP or modified versions of ACP as a filler phase, we have prepared

photopolymerizable bioactive composites that had adequate physicochemical and mechanical properties and

their bioactivity resides in the remineralization potential of

ACP as a consequence of the sustained release of calcium

and phosphate ions into simulated saliva media.

However, compared to conventional glass-filled composites, ACP composites are still relatively weak in mechanical

strength. In an effort to improve their reinforcing capabilities, we have modified ACP during its synthesis with

glass-forming agents such as tetraethoxysilane (TEOS)

and zirconyl chloride. This has resulted in modest improvement of mechanical properties, such as biaxial flexure

strength. Further improvements may be feasible by the use

of coupling agents with these modified ACP fillers and

alternative matrix resins. Another strategy for enhancing

mechanical properties is to employ hybrid filler phases

consisting of ACP filler admixed with silanized glass fillers

and/or polymer fibers, such as oriented polyethylene

fibers. Preliminary studies have yielded encouraging results for all these strategies.

These studies also have shown that certain variations in

methacrylate resin chemical structure and composition

Bioactive Polymeric

Composites for

Mineralized Tissue

Regeneration

Joseph M. Antonucci

Crystalline hydroxyapatite (HAP) is considered to be the

final stable product in the precipitation of calcium and

phosphate ions from neutral or basic solutions and it is

also the structural prototype of the major mineral component of bones and teeth. Recently, there has been increasing interest by biomaterials community in utilizing polymers of various types as matrices and as reinforcements

(especially in fiber forms) for calcium phosphate-based

composites. Customers for this technology include dental

and biomedical manufacturers and practitioners.

may affect the rate and extent of the ion release from ACPfilled composites, the internal conversion of ACP into

HAP, the conversion of methacrylate groups, as well as

the mechanical properties of the composites.

Recent studies have involved assessing the effect of

substituting ethyl-α-hydroxymethylacrylate (EHMA) for

HEMA. EHMA, a unique isomer of HEMA, is much more

hydrophobic than the completely water miscible HEMA.

Preliminary results indicate that ACP composites utilizing

EHMA are significantly stronger than similar composites

based on HEMA. In related research, a facile synthesis

has been developed for new types of low-shrinking,

crosslinking monomers of controlled biodegradability and

hydrophilicity that also enable high loadings of ACP in

composites.

These various types of polymeric calcium phosphate

materials are designed to be bioactive, biocompatible and

highly conformable to mineralized tissue. Injectable,

photopolymerizable ACP composites appear feasible as

well. All these ACP composites are expected to have significant remineralization potential and should find use in

remineralizing white spots and caries lesions in tooth

structure, especially interproximally and gingivally. If

successful, ACP composites would have significant advantages over other remineralizing therapies. Currently, a

strong need exists for protective liners, bases, prophylactic sealants and adhesive restoratives that are manipulated

easily and that can provide efficacious long-term protection against demineralization and even have

remineralization capabilities. In addition, bioactive ACP

composites with biodegradable polymer matrices may

find wider applications as therapeutic materials with the

ability to provide osteoconductive environments conducive to promoting bone healing, such as is needed in

dental (endodontic, periodontal etc.) and other biomedical

applications.

J.M. Antonucci, M.D. Weir, C.A. Khatri, E.D. Eanes, B.O. Fowler (Polymers

Division, NIST)

D. Skrtic, G.E. Schumacher (American Dental Association Health Foundation

Paffenbarger Research Center)
Contact Information:

31

Materials for Microelectronics

Today’s U.S. microelectronics and supporting infrastructure industries are in fierce international competition to

design and produce new smaller, lighter, faster, more functional, and more reliable electronics products more quickly

and economically than ever before.

Recognizing this trend, in 1994 the NIST Materials Science

and Engineering Laboratory (MSEL) began working very

closely with the U.S. semiconductor, component and packaging, and assembly industries. These early efforts led to

the development of an interdivisional MSEL program

committed to addressing industry’s most pressing materials measurement and standards issues central to the development and utilization of advanced materials and material processes within new product technologies, as

outlined within leading industry roadmaps. The vision that

accompanies this program—to be the key resource within

the federal government for materials metrology development for commercial microelectronics manufacturing—may

be realized through the following objectives:

• Develop and deliver standard measurements and data;

• Develop and apply in situ measurements on materials

and material assemblies having micrometer- and

submicrometer-scale dimensions;

• Quantify and document the divergence of material

properties from their bulk values as dimensions

are reduced and interfaces contribute strongly to

properties;

• Develop models of small, complex structures to substitute for or provide guidance for experimental measurement techniques; and

• Develop fundamental understanding of materials

needed in future microelectronics.

With these objectives in mind, the program presently

consists of 20 separate projects that examine and inform

industry on key materials-related issues, such as: electrical, thermal, microstructural, and mechanical characteristics of polymer, ceramic, and metal thin films; solders,

solderability and solder joint design; photoresists, interfaces, adhesion and structural behavior; electrodeposition, electromigration and stress voiding; and the characterization of next generation interlevel and gate dielectrics.

These projects are conducted in concert with partners

from industrial consortia, individual companies, academia,

and other government agencies. The program is coupled

strongly with other microelectronics programs within

government and industry, including the National Semiconductor Metrology Program at NIST.

FY2001 Projects (and division leading project)

Lithography/Front End Processing

Characterization of Ultrathin Dielectric Films (Ceramics)

Lithographic Polymers (Polymers)

On-chip Interconnects

Interconnect Materials and Reliability Metrology (Materials Reliability)

Measurements and Modeling of Electrodeposited Interconnects (Metallurgy)

Thin Film Metrology for Low-k Dielectrics (Polymers)

Packaging and Assembly

Packaging Reliability (Materials Reliability)

Solder Interconnect Design (Metallurgy)

Solders and Solderability Measurements for Microelectronics (Metallurgy)

Tin Whisker Mechanisms (Metallurgy)

Wafer Level Underfill Experiment and Modeling

(Metallurgy)

Wire Bonding to Cu/Low-k Semiconductor Devices

(Metallurgy)

X-ray Studies of Electronic Materials (Materials

Reliability)

Crosscutting Measurements

Dielectric Constant and Loss in Thin Films and Composites (Polymers)

Electron Beam Moiré (Materials Reliability)

Ferroelectric Domain Stability Measurements (Ceramics)

Measurement of In-Plane CTE and Modulus of Polymer

Thin Films (Polymers)

Mechanical Properties of Thin Films (Ceramics)

Permittivity of Polymer Films in the Microwave Range

(Polymers)

Polymer Thin Films and Interfaces (Polymers)

Texture Measurements in Thin-Film Electronic Materials

(Ceramics)

Thermal Conductivity of Microelectronic Structures (Materials Reliability)

Wen-li Wu
Materials For Microelectronics

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As integrated circuit feature sizes continue to shrink, new

low-k interlevel dielectric materials are needed to address

problems with power consumption, signal propagation

delays, and crosstalk between interconnects. One avenue

to low-k dielectric materials is the introduction of nanometer-scale pores into a solid film to lower its effective

dielectric constant. Specifics of the pore architecture may

affect other properties, hence characterization of the pore

structure of thin nanoporous low-k dielectric films is critical and beyond the capabilities of conventional methods.

The small sample volume of 1-μm films and the desire to

characterize the film structure on silicon wafers narrow the

number of available measurement methods. We have developed a novel combination of small-angle neutron scattering (SANS), high-resolution x-ray reflectivity (HRXR),

and ion scattering techniques to determine important

structural and physical property information about thin

porous films less than 1 μm thick. These measurements are

performed directly on films supported on silicon substrates so that effects of processing on structure can be

investigated.

During the past year, we focused efforts in three areas:

continuing characterization of current industrially relevant

materials through International SEMATECH, establishing

new collaborations with Rohm and Haas and Dow Chemical, and developing advanced measurement methods for

more thorough and accurate film characterization. International SEMATECH, a consortium of microelectronics companies, provided more than 20 separate samples for characterization by NIST, including spin-on glass materials,

films from chemical vapor deposition, and organic thin

films. The structural information provided by NIST is

placed into a master database that includes data from a

variety of sources, detailing both the structural and material properties needed to evaluate candidate materials.

New measurement methods have been developed to more

thoroughly and accurately characterize pore and matrix

morphology. HRXR measures the average film thickness

and average density of the wall and voids. By infusing

Characterization of

Porous Low-k Dielectric

Constant Thin Films

NIST is providing the semiconductor industry with

unique on-wafer measurements of physical and structural

properties of porous thin films important as low-k

interlevel dielectric materials. The methodology uses

several complementary experimental techniques to measure the average pore and matrix morphology, including

pore size distributions. New methods have been developed to measure pore and matrix morphology in films

having complex structures.

Barry J. Bauer, Eric K. Lin, Wen-li Wu

toluene into the voids, the volume fraction of connected

voids can be measured by HRXR along with the average

density of the wall material and closed pores. When the

toluene vapor is lower than the saturated vapor pressure

(partial pressure), the small pores fill first, and measurement of the overall density by HRXR allows calculation of

the complete pore size distribution.

Other new techniques being developed include SANS

measurements on films that have been infused with mixtures of normal toluene and deuterated toluene. The match

point measures where the neutron contrast of the toluene

matches that of the wall material. This measures porosity

and wall density in a way that is independent from the

HRXR measurements and applies to all morphology types.

When the match point has been determined, the films can

be infused with the match mixture at various partial pressures in a way analogous to the HRXR. Pore size distributions can be estimated from the partial pressure SANS,

and at the saturation point, any residual scattering present

gives information on sample heterogeniety.

Figure 1. Representative pore size distribution calculated

from HRXR partial pressure measurements.

B.J. Bauer, E.K. Lin, H. Lee, H. Wang, R. Hedden, D. Liu, W.L. Wu (Polymers

Division, NIST)

J. Wetzel, J. Lee (International SEMATECH), N. Pugliano (Rohm and Haas),

B. Landes (Dow Chemical), M. Baklanov (IMEC), D. Gidley (University of Michigan), W. Chen, E. Moyer (Dow Corning), S. Yang (Lucent) H. Fan, C.J. Brinker

(Sandia National Laboratory)
Materials For Microelectronics

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Polymer Fundamentals of

Photolithography

Eric K. Lin, Wen-li Wu

E.K. Lin, C.L. Soles, J.L. Lenhart, R.L. Jones, P.M. McGuiggan, D.L. VanderHart,

W.L. Wu (Polymers Division, NIST)

D.A. Fischer (Ceramics Division, NIST)

D.L. Goldfarb, M. Angelopoulos (IBM T.J. Watson Research Center)

In photolithography a pattern is transferred to the silicon

substrate by altering the solubility of areas of a polymeric

photoresist thin film exposed to light through a mask via an

acid catalyzed deprotection reaction. To fabricate smaller

features, next-generation photolithography will be processed with wavelengths of light requiring photoresist

films less than 100-nm thick and dimensional control to

within 2 nm. Many new material and transport issues arise

when fabricating structures over these length scales.

To advance this key technology, we work closely with

industrial collaborators to apply high-spatial resolution and

chemically specific measurements to understand varying

material properties and process kinetics at nanometer

scales. The unique measurement methods we apply include

x-ray (XR) and neutron reflectivity (NR), small-angle neutron scattering (SANS), incoherent neutron scattering

(INS), near-edge x-ray absorption fine structure (NEXAFS),

and combinatorial methods. Our efforts focused on the

fundamentals of polymer materials and processes that

control the resolution of photolithography including: (1)

the physical properties and polymer chain conformation

within sub-100-nm structures; (2) the spatial segregation

and distribution of photoresist components; (3) the transport and kinetics of photoresist components and the

deprotection reaction interface; and (4) the structural characterization of lithographically prepared structures.

This past year, we made significant progress in elucidating molecular behavior of important lithographic processes. We performed the first measurements of the threedimensional conformation of polymer chains (SANS) and

the local dynamics of model photoresist polymers (INS)

confined in sub-100-nm thin films. These results provide

important insight into observed deviations in material properties and transport processes within sub-100-nm imaging

layers needed in the future (see Accomplishment Report

“Measurement Methods Aid Development of Photoresists

for Next-generation Photolothography”).

Using NR and XR, we have shown that moisture uptake in

photoresist films (a critical component in some resists) is

Photolithography, the process used to fabricate integrated circuits, is the key enabler and driver for the

microelectronics industry. As lithographic feature sizes

decrease to the sub-100-nm length scale, significant

challenges arise because both the image resolution and

the thicknesses of the imaging layer approach macromolecular dimensions characteristic of the polymers used in

the photoresist film. Unique high-spatial resolution measurements are developed to reveal limits on materials

and processes that challenge the development of photoresists for next-generation sub-100-nm lithography.

uniform, not segregated to a hydrophilic or hydrophobic

substrate. Additional NR measurements (Figure 1) show

the interfacial development of partially miscible polymer

layers (similar to soluble and insoluble areas of an exposed

resist) with nanometer resolution. We have applied

NEXAFS to measure the distribution of photoacid generator molecules within the top (2–3) nm of the resist film

relative to the bulk concentration. The surface segregation

of important resist components and the resulting chemistry strongly affect the quality of the fabrication process.

SANS measurements of lithographically prepared structures have been extended and applied to new photoresist

formulations and structural sizes. Finally, we are applying

combinatorial methods to quantify quickly important temperature boundaries in the compositional dependence of

the thermal deprotection of photoresist polymers mixtures.

Figure 1. Neutron reflectivity data and real space profiles

from bilayers of deuterated poly(methyl methacrylate) and

poly(hydroxystyrene). The data show the interfacial evolution over nanometer-length scales.
Materials For Microelectronics

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Characterizing Buried

Polymer/Substrate

Interfaces

Joseph L. Lenhart

J.L. Lenhart, J.P. Dunkers, W.L. Wu (Polymers Division, NIST)

R.S. Parnas (currently at University of Connecticut), J.H. van Zanten (North Carolina State University).

The measurement system consists of chemically attaching

a fluorophore, dimethyl-amino-nitro-stilbene (DMANS) to a

triethoxy silane-coupling agent, generating a fluorescently

labeled silane-coupling agent (FLSCA) that bonds with

hydroxyl groups on glass or metal surfaces. FLSCA-coated

glass surfaces were immersed in epoxy resin. A blue shift in

the emission maximum from the fluoroprobe and an increase in fluorescence intensity could be measured during

resin cure. Since the DMANS probe is grafted into the

silane layer, the fluorescence response is completely from

the interfacial region. FLSCA was diluted on glass surfaces

While many techniques are available to study polymer

films and surfaces, very few can probe buried polymer/

substrate interfacial regions, which are critical in composites, nano-composites, biomaterials, electronics,

paints, coatings and adhesives. A technique was developed to probe this interfacial region by localizing a

fluorescent dye on the substrate surface. The current

work is focused on applications to glass-reinforced

composites, but the technique will be extended for

micro-electronics applications to probe interfacial

acidity of photo-resist polymers adhered to bottom antireflective coatings.

independent of the FLSCA/GPS layer thickness (right

most graph below). These data show that the composition profile in the interfacial region is influenced by the

competition between diffusion of resin monomers into the

silane layer, and the reaction kinetics, which slow the

diffusion process. Using the transition from incomplete

penetration (0.5-μm thick layers) to complete penetration

(0.3-μm thick layers), the diffusion constant for resin

monomers into the silane layer was estimated to be in the

range of (10-12 to 10-13) cm2

/s estimated from D~L2/tgel,

where tgel is the resin gel time. The dotted lines represent

the total fluorescence shift when the layers were immersed in hardener only. Since the amine on the hardener

will react with the epoxy functionality these lines represent the maximum fluorescence shift that is expected from

equilibrium penetration of the resin and silane layer. The

work has resulted in several publications (J. Coll. Interface Sci. 221, 75, 2000; Langmuir 16, 8145, 2000; Macromolecules 34, 2225, 2001; Optics & Lasers Eng. 35, 91,

2001; Polymer Composites, in press; J. Coll. Interface

Sci., submitted).

The technique will be extended to interfaces in microelectronics including the photoresist and anti-reflective coating (ARC) interface. To probe the acidity in the interfacial

region, acid sensitive fluorescent probes will be grafted to

the ARC layer.

with glycidoxypropyltriethoxysilane (GPS), a coupling

agent used as a surface primer in glass fiber-reinforced

composites. Experiments were conducted as a function of

the FLSCA/GPS layer thickness. The thickest silane layer

exhibited a smaller fluorescence shift during cure, suggesting incomplete resin penetration into these layers (see

right). The resin was composed of a stochiometric mixture

of diglycidyl-ether-bisphenol A (DGEBA) cured with a

diamine hardener polypropylene-glycol-bis-2-aminopropyl

ether (Jeffamine D400 or D230). Two molecular mass

Jeffamine hardeners were used (230 and 400) g/mole. The

DGEBA/D400 system gelled in 30 min, while the DGEBA/

D230 resin system gelled in 15 min. When the slower gelling resin was used, the fluorescence shift during cure was
Contact Information:

35

Materials for Wireless Communication

Today, wireless technologies constitute one of the most

important growth areas in the global electronics industry.

The current revolution in wireless communications would

not have been possible without the discovery and development of oxide ceramics exhibiting the coincidence of

high, temperature-independent resonant frequency with

low dielectric loss. Technically important ceramic materials

fall into two major dielectric categories: bulk ceramics for

base station resonators/filters and those needed for lowpower, miniaturized hand-held devices. Paramount in

achieving smaller and lower cost devices are guidelines

that facilitate the rational design of advanced materials

to provide temperature stability, frequency, and sizereduction requirements for the next generation of devices

for cellular, PCS, and many other niches of the wireless

communications industry.

A collaboration between the Ceramics Division and the

Electrical and Electronics Engineering Laboratory at NIST

on ceramic materials for base station applications includes

experimental determination of selected complex-oxide

phase diagrams integrated with in-depth structural (x rays,

electrons, neutrons), crystal-chemical, spectroscopic, and

dielectric property characterization. The objective of this

multidisciplinary project is to determine the fundamental

relationships between phase chemistry, crystal structure,

and dielectric performance at wireless frequencies.

Another project in the Ceramics Division uses firstprinciples calculations to elucidate the roles of cation

order-disorder and ferroelastic phenomena in determining

the phase relations and physical properties of complex

ceramic oxide systems. These calculations are used to

predict cation ordering phenomena, physical properties,

and how they vary with chemical composition. Critical

experiments are performed to test the predictions.

Microstructural modeling and experimental studies are

also under way to determine the dimensional changes in

low-temperature-cofired ceramics used for portable communication devices. Processing models were identified by

a large segment of industrial producers as being crucial to

reducing the time currently needed to design and produce

components. Wireless devices, often hand-held, are especially susceptible to mechanical damage; assuring the

reliability of electronic products is especially critical for

such devices. Work in the Materials Reliability Division

includes development of noncontact acoustic metrology

to characterize wireless materials in both thin-film and bulk

form. Also, the mechanical properties of thin films are

investigated using laser-ultrasonic methods to generate

and detect surface acoustic waves. The elastic property

information obtained will result in improved predictive

modeling of film performance. In addition, resonantultrasonic techniques are applied to new piezoelectric

materials for SAW devices, used extensively as oscillators

in hand-held devices.

Researchers in the Polymers Division developed a new

test method that permits dielectric measurements of film

substrates at frequencies of 1 to 10 GHz. The project is

exploring the relationships between dielectric properties

and structure in a variety of polymer resins, blends and

composites, e.g., hybrid materials based on polymer resins

and ferroelectric ceramics. Microstructural modeling and

experimental studies are being undertaken to determine the

effect of polarizability of the polymer matrix on the apparent dielectric permittivity of the composite. A need for

models and measurement techniques has been identified

by a large segment of industrial producers as being crucial

in new designs and in reducing the development time of

new products. A consortium involving the National Center

for Manufacturing Science (NCMS) and industry has been

organized to help address these issues.

David J. Vanderah
Materials For Wireless Communication

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Novel dielectric hybrid materials based on organic resins

and ferroelectric ceramics with high-dielectric constants

are being developed by the industry to advance miniaturization and functional performance of high-speed electronics. These materials are being used to construct integrated

passive devices and de-coupling capacitance films with

low impedance that are embedded within chip substrates

and printed circuit sub-assemblies. This new material

approach is essential as current methods based on discrete components cannot provide adequate solutions at

frequencies above 1 GHz, which are critical for wireless

communications technologies. The goal of this project is

to provide the microelectronics industry with an accurate

measurement technique of permittivity for dielectric films

at microwave frequencies above 1 GHz and to develop a

fundamental framework to identify the key structural and

molecular attributes that control dielectric properties of

polymer composites.

Dielectric Metrology for

Polymer Composite Films

in the Microwave Range

Development of the Integrated Passive Device technology

for high-speed electronics critically depends on the ability to measure the dielectric permittivity and on the ability to control the dielectric properties from the material’s

microstructure. This project provides the microelectronics industry with an accurate technique to measure permittivity at microwave frequencies and a fundamental

framework to identify the key structural and molecular

attributes that control dielectric properties of polymer

composite films.

Jan Obrzut

During the past year we focused on a broadband measurements procedure for film substrates that would be suitable

for adaptation as a new industry standard method. The

test methods currently in use are lumped-element approximations limited to frequencies below a few hundred megahertz, especially in the case of high-dielectric constant

films. Our new broadband measurement methodology is

based on observation and analysis of the fundamental

propagation mode in a film specimen terminating a coaxial

transmission line. Using this test technique, the impedance characteristic and the dielectric permittivity of highdielectric constant films can be accurately measured at

frequencies from 100 MHz to 10 GHz with the precision

required by wireless technologies (Figure 1). To enable

measurements at frequencies above 20 GHz we are collaborating with the NIST Radio Frequency Division on full

mode analysis.

In partnership with the IPC Standard Test Committee

Task Force for Embedded Passive Devices we designed

the standard test protocol and made arrangements with

co-sponsoring member companies for round-robin

evaluation.

This project also explores the relationships between dielectric properties and structure in polymer resins, blends

and composites. The microwave dielectric properties of

several polymer-ferroelectric ceramics composites have

been evaluated. Microstructural modeling and experimental studies are under way to determine the effect of polarizability of the polymer matrix on the apparent dielectric

permittivity of the composite.

Models and measurement techniques developed in this

study were identified by a large segment of industrial

producers as being crucial in material design and ing reducing the development time of new products.

Figure 1. Broadband impedance data for polymer composite film having permittivity of 34.6 – j 1.6. (a) conventional

results (b) results calculated for a thin-film capacitance,

(c) determined by our new testing procedure .

J. Obrzut, N. Noda, C.K. Chiang, C.L. Soles, D.L. VanderHart (Polymers Division, NIST)

J. Baker, R. Gayer, P. Kabos, B. Riddle (Radio Frequency Technology Division, NIST)

J. Lauffer (IBM), D. Murry (Litton), R. Charbonneau (Storage Tech.), R. Foly (DOD), L.

Patch (NCMS), D. McGregor (DuPont), D. Senk (Shipley), R. Sheffield (Nortel), A.

Tungare (Motorola), J. Koh (IPC)
Contact Information:

37

Multiphase Polymeric Materials

The Multiphase Polymeric Materials Program develops

realistic measurement and characterization platforms for

multiphase polymeric materials that use a combination of

experimental measurements and theory and modeling tools

to provide realistic and highly optimized output. These

measurement and characterization tools and platforms are

intended to help industries in pre-production evaluation,

materials characterization, and performance prediction, as

well as to provide data for process design.

In order to achieve the performance requirements in modulus, stiffness, toughness, temperature, chemical and environmental stability, desired appearance and touch, most

polymeric materials in use are either phase separated

blends with two or more components, and/or filled with

particles or short/long fibers. The challenge in using

multiphase polymeric materials extends from processing

design, through structure and properties prediction and

characterization, to service life prediction. This program is

designed to use theoretical and computational modeling

tools in conjunction with characterization measurements

to form realistic and workable tool sets.

Specifically, characterization techniques will be developed

and used to generate relevant databases or constitutive

relations to be used as input for more realistic theory and

modeling and to bridge the gap in current tools. Current

theoretical and computational tools are capable of modeling fine length scales such as nanoscale molecular dynamics simulations, microscale self-consistent field or density

functional methods, and meso-scale time dependent

Ginsburg-Landau or Cahn-Hilliard-Cook techniques. On

the other hand, macroscopic part sized finite-element-flow

calculations and Object Oriented Finite element analysis

(OOF) for properties calculations and virtual testing are

much coarser grained tools. A seamless connection between these two sets of computer tools is not available to

provide realistic materials properties for design, prediction

and characterization.

This program is working currently on three materials characterization projects to provide:

(1) phase separation/crystallization results together with

interfacial characterization and rheological data to form

constitutive relations as input for finite-element-flow modeling, and characterization of phase structure;

(2) structure, dynamics, and modulus characterization in

high surface area particle-filled polymers and blends for

performance characterization and validation of multiscale

computer modeling; and

(3) fiber tow characterization and failure results as input to

finite-element-based mechanics and performance evaluation. All three projects are linked to future applications of

OOF to polymer research on property prediction and virtual testing.

MSEL researchers work with industrial partners through

informal collaborations, Cooperative Research and Development Agreements (CRADAs), and consortium arrangements. Industrial partners include resin suppliers, system

suppliers, parts producers, members of the automotive

industry, and offshore oil platform companies.

Charles C. Han
Multiphase Polymeric Materials

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Constitutive Relationship

of Polymer Blends for

Process Modeling Needs

Howard Wang, Charles C. Han

H. Wang, C.C. Han, K. Shimizu, G.Z.G. Wang, H. Kim, E.K. Hobbie (Polymers Division, NIST)

B.S. Hsiao (SUNY), D. Lohse (EXXON)

The first stage of this project is to obtain detailed and quantitative understanding of the phase transitions in a

polyolefin blend. Then the focus will shift to the dynamics

of phase separation in the presence of crystallization and

non-equilibrium phase behavior under shear flow. A pair of

commercial olefin polymers, metallocene-catalyst synthesized statistical copolymers of ethylene/hexene (PEH) and

ethylene/butene (PEB), were selected as model materials.

The PEH component is crystallizable. Research on the

model system results in the following findings:

Measurement of Phase Transitions

Modified optical techniques were used to identify the

boundary of liquid-liquid phase separation (LLPS) because

the almost identical refractive index of the blends components and slow kinetics made conventional optical methods

difficult. The LLPS boundary has been determined using

crystallization induced contrast. Incoherent and coherent

light scattering, light transmission, atomic force microscopy

(AFM) and differential scanning calorimetry, are used to

exploit the crystallization morphology from previously homogenous or segregated blends. The blend exhibits an

upper critical solution temperature of 146 o

C. The composition dependence of the LLPS boundary follows the prediction of Flory-Huggins theory for binary polymer mixtures.

The equilibrium melting temperature of the blends decreases

from 145 o

C for pure PEH with increasing PEB concentration

in the miscible phase, whereas it remains relatively constant

within 2-phase region (figure left).

Process modeling may facilitate design of optimal conditions for processing polymer blends provided that the

complex structure and behavior of these materials are

treated adequately. Techniques and methodologies are

developed to define and characterize necessary rheological, morphological and interfacial properties for multiphase polymer blends as a function of processing parameters, composition, phase miscibility, and crystalline

structure growth. Constitutive relationships are formulated either as a database or in combination with analytical expressions for process modeling needs.

Competing Kinetics

The kinetic interplay between crystallization and phase

separation in a polymer blend has been examined. By

controlling the relative quench depths for liquid-liquid

phase separation and crystallization, the growth kinetics

of the characteristic length scales of the simultaneous

ordering processes show a crossover from crystallization

dominated to phase-separation dominated behavior. Based

on a scaling argument for late-stage spinodal decomposition, we conclude that this kinetic crossover is inevitable

in a blend for which the critical temperature of liquid-liquid

phase separation is above the equilibrium melting temperature of the blend, as shown in the figure below.

Crystallization Morphology

Morphology development during competing LLPS and

crystallization, and during crystallization in a previously

segregated blend, either under quiescent conditions or

under shear flow, is investigated using time-resolved

small-angle light scattering, time-resolved small- and wideangle x-ray scattering (SAXS and WAXS), optical microscopy (OM), and AFM. To date, comprehensive OM,

SAXS and WAXS measurements on pure PEH and critical

blends at different isothermal temperatures have been

completed. AFM measurements on crystal morphology at

selected temperatures are also made.
 Multiphase Polymeric Materials 

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We currently are engaged in a project to predict the microstructure that forms during the injection molding of polymer blends. Blend mixtures usually enter an injection molding cavity, well mixed and quenched, from an extruder.

However, upon entering the cavity, the drops are highly

sheared and break-up into finer and finer sizes near mold

walls, and coarsen towards equilibrium sizes in regions of

low shear. This leads to a non-uniform “skin-core” microstructure in the final part, which highly affects the properties. In order to predict the properties, one must be able to

model the morphology that develops during flow. Our

approach to this problem involves modeling flow at several length scales. Microscale models which simulate

multiphase flow are used to predict detailed drop morphology. However, such models are too computationally demanding to model an entire injection molding process.

Thus, volume averaged macroscale models, which use

phase-averaged materials properties and micromodels to

predict average material structure, are used to predict mold

filling. By using such models in tandem, one can get a

good approximate picture of the drop morphology.

Complementing model development, experimental work

Modeling of Interfaces

and Interphases of

Polymeric Systems

Frederick R. Phelan Jr., Erik K. Hobbie,

Charles C. Han

A computational software tool is developed for predicting

the microstructure evolution of polymer blends in injection molding operations for industrial users. The injection

molding of polymer blends is carried out generally while

the components are phase separated in which drops of

one phase are dispersed in a matrix phase. The detailed

morphology that develops during flow depends on the

fluid mechanical deformation history, component rheological properties, and blend thermodynamics. The utility

of the computational method is enhanced through a fundamental understanding of the interplay between the

various process parameters and blend microstructure.

provides viscosity and drop size measurements as a function of shear rate and composition in blend mixtures.

Progress in modeling microstructure evolution resulted

from a microflow simulation for binary mixtures based on

the multiphase momentum balance and a Ginzburg-Landau

free energy for the chemical potential in the chemical species balance. The model equations are solved together with

the continuity equations, using a spectral finite element

method. Figure 1 shows the evolution of a randomly dispersed initial phase into a discrete layered structure during

shear flow. In the absence of flow the initial state coarsens

into discrete drops. The simulation shall be extended to

non-Newtonian flows in the next phase of the work.

An experimental component of this project is an exhaustive

rheo-optical study of a variety of polymer blend systems

under simple shear flow. By varying such parameters as the

viscoelasticity of the components, the proximity to a critical

point, and the interfacial tension between the phases, we

are accumulating an experimental database to help guide

these simulations. The primary measurement techniques are

light scattering, optical microscopy and rheometry.

F.R. Phelan Jr., E.K. Hobbie, H. Wang, C.C. Han (Polymers Division, NIST)

T. Nguyen (Building and Fire Research Laboratory, NIST)

S. Glotzer (University of Michigan), Polymer Interphase Consortium (NIST, Dow

Chemical, PPG, Visteon)

Figure 1. Evolution of binary microstructure during shear flow. (Left) Initial condition: randomly dispersed two-phase

structure. (Right) Near steady state under shear flow, the phases form a layered structure.
Multiphase Polymeric Materials

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40

Shear-induced structural ordering in materials containing

clay is a new problem encountered in nanocompositebased materials. The shear orientation of viscoelastic

polymer-clay solutions was studied by means of rheology,

flow birefringence and small-angle neutron scattering

(SANS) under shear. The polymer chains are in dynamic

adsorption/desorption equilibrium with the clay particles

to form a “network”. The elastic behavior of the network

was characterized by constant stress, oscillatory shear,

and stress relaxation experiments. Experiments under

steady flow characterized the transient behavior of the

network. With increasing steady shear rate a pronounced

minimum in birefringence was observed at a critical shear

rate showing that clay platelets orient first, then polymer

chains start to stretch. The shear rate dependent viscosity

exhibited near power-law behavior and no corresponding

critical feature. While birefringence detects orientational

effects on a microscopic-length scale, rheology averages

over macroscopic changes in the sample. The same degree

of orientation could be achieved under constant shear rate

or constant stress conditions.

Simulations of a polymer melt surrounding a symmetric

nano-particle have already shown the important role played

by nano-particle/polymer interactions on the changes in the

structure, dynamics, and glass transition of the melt. Continued work on these systems shows the importance of

changes in the surface goemetry and the surface-to-volume

ratio on the relaxation of chains near the surface. Simulations focused on larger systems are probing the role interactions play in the dynamic clustering and dispersion of

nano-particles within the melt. Our results indicate that

clustering is very sensitive to changes of both the particle/

particle and particle/polymer interactions. Additionally,

shear flow, such as that experienced during injection molding, can alter the clustering properties of the particles.

Finally, these particles also alter the blend phase diagram,

an area of future consideration. Separately, we have also

undertaken simulations of a carbon nanotube filled polymer

melt in an effort to explore changes introduced by filler

asymmetry.

Synergistic Interactions

in Polymer-Nanoparticle

Composites

Inorganic fillers frequently are used to enhance polymer

properties. New attributes may be achieved with

nanoparticulates provided that the underlying science is

developed. Polymer nanocomposites are important in

many diverse industrial processes. Potential applications

derived from synergistic behaviors and hybrid properties

of polymer-nanoparticle composites include data storage

and optical and electro-rheological materials for display

devices. The objectives of this project are to set new directions and provide fundamental understanding of polymernanoparticle interactions and how they dictate the properties of different materials.

Gudrun Schmidt, Francis W. Starr,

Erik K. Hobbie, Charles C. Han

Figure 1. Concentration dependence of SANS intensity

from polymer-clay nanocomposite samples is correlated

with AFM. LRD2-bulk (40% PEO, 60% clay) and LRD5-

bulk (63 percent PEO, 37 percent clay).

Figure 2. Snapshot of molecular dynamics simulation

showing a configuration of dispersed nano-fillers embedded in polymer melt.

G. Schmidt, F.W. Starr, E.K. Hobbie, C.C. Han (Polymers Division, NIST)
 Multiphase Polymeric Materials 

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To achieve the goals of the project, research is conducted in

three tasks. First, techniques are developed to characterize

the microstructural features in complex multicomponent

polymeric systems. Second, existing measurement techniques are adapted or new methods are generated to determine properties in materials with complex microstructure.

Finally, models are formulated to relate the performance of

such materials to the properties of their constituents and

the microstructure that is present. Where appropriate, Object Oriented Finite Element Analysis (OOF) is employed to

incorporate the measured microstructure into the models.

The methods developed in the three tasks then are applied

to model systems that are relevant to industrial needs.

Hybrids are polymers reinforced with two or more different

types of continuous fibers. By combining two fibers it is

often possible to achieve significantly better trade-offs

among various properties and between cost and performance. For this reason, hybrids are a prime candidate for

use by the construction industry in composite bridge design and by the oil industry in off-shore drilling platforms.

NIST is working with the Composites Engineering and

Applications Center at the University of Houston to bridge

the gap between laboratory tests and industrial applications. Recent results in this program are discussed below.

Structure-Property

Characterization and

Modeling

The goal of this project is to provide industry test methods, reference data, and predictive models for advanced

polymeric material by understanding the role of microstructure in performance. This technology will enable

fabricators and users of these materials to develop superior products for applications in transportation, infrastructure, aerospace, and off-shore oil exploration.

Microstructure Determination: Microscopy has been used

to determine fiber arrangement, void content, and void

distribution in hybrid composites, but fiber concentration

and mix are difficult to quantify. Consequently, a modification to the burn-off test was developed to assess these

features. The procedure has been verified with tests on

samples of known concentrations (see figure left).

Test Method Development: The Iosipescu test was used to

measure the shear moduli of hybrid composites. This test

has now been used to characterize the behavior of the

model hybrid composites that were characterized in the

Microstructure Determination task. Tensile properties were

also determined.

Modeling: To predict the moduli determined above, a towbased finite element model was developed. Based on properties of the constituents, both the tensile and shear moduli

were modeled successfully as shown in above figure. The

actual microstructures determined in the Microstructure

Determination Task were used in the model. The work is

now being extended to failure behavior. With a tow-based

approach, the complete stress strain curve for this sample

could be predicted based on the behavior of a single glass

and a single carbon fiber.

Donald L. Hunston, Charles C. Han

D.L. Hunston, W.G. McDonough, J. He, M. Chiang, C.C. Han (Polymers Division,

NIST)

Lincoln Composites, OSI, Owens Corning, Composites Engineering and Application Center, Cornell University
Multiphase Polymeric Materials

Contributors

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Collaborators:

42

It is recognized that single fiber tests are inadequate in

predicting failure in 3-dimensional structures. Our efforts

are transitioning from 2-D multi-fiber arrays to 3-D fiber

arrays. The current data, however, focuses only on 2-D

multi-fiber model composites.

In Figure 1, the inter-fiber spacings between four of the five

fibers in a 2-D array are between (1.4 to 1.5) fiber diameters.

Capitalizing on optical coherence tomography’s (OCT’s)

unique ability to see changes in matrix stresses, the area

immediately surrounding the fibers (> 2 fiber diameters) was

observed to have a different intensity than the bulk resin

(< 2 fiber diameters). This intensity change reflects the

residual curing stresses that occur due to the close proximity of the fibers. This change in intensity is not observed in

single-fiber fragmentation specimens.

Mechanics of Fiber and

Nano-Filled Composites

Gale A. Holmes, Charles C. Han

Failure prediction is critical to the use of fiber-reinforced

composites in many applications. Multi-fiber model composites are being used to conduct fundamental studies

into the nucleation of failure in fibrous composites. Current results have revealed that the nucleation of critical

flaws in unidirectional fibrous composites may depend

on the time-dependent redistribution of stress by the

viscoelastic matrix. Although their role in flaw nucleation is not understood clearly, shear deformation bands

have been detected between fiber breaks and residual

curing stresses have been detected in the matrix by optical coherence tomography.

Consistent with epoxy-compatible industrial coatings, the

11-AUTCS coating exhibits matrix crack formation in addition to fiber-matrix debonding during fiber fracture. Initial

investigations revealed the presence of 45o

 shear deformation bands emanating from the crack tips when specimens

are under tensile load (see Figure 2). The shape of the

matrix cracks surrounding each fiber break is similar to unsymmetrical penny-shaped cracks. It is known that pennyshaped cracks in a material subjected to uniaxial tensile

loads generate 45o deformation shear bands that form relative to the tensile axis at the crack-tip. The deformation

bands emanating from the crack tips in Figure 2 may relate

to this phenomenon. The location of the penny-shaped

flaws within the composite is controlled by the spatial

population of flaws in the embedded fiber and the stress

transfer efficiency at the fiber-matrix interface. The influence

of these shear bands on the non-aligned fiber break patterns shown in the figure is not known. It is believed at this

point that these bands may be an important key to understanding the role that the viscoelastic matrix plays in nucleating critical flaws in fibrous composites.

G.A. Holmes, C.C. Han, W.G. McDonough, J.P. Dunkers, E.B. Feresenbet (Polymers

Division, NIST)

L. Phoenix (Cornell University), D. Raghavan (Howard University), J. Nairn

(University of Utah), Eric Pohl (Witco Chemicals)

Figure 1. Isosurface plot of a multiple E-glass fibers (blue)

embedded in DGEBA/m-PDA matrix (red). Green region

surrounding the fibers denotes residual curing stresses.

Data obtained using optical coherence tomography.

The initial 2-D multi-fiber arrays consisted of embedded

fibers coated with 11-aminoundecyl trichlorosilane (11-

AUTCS) deposited using self-assembled monolayer (SAM)

technology. The SAM technology is being used in a

companion micromechanics project to probe the effect of

covalent bonding, mechanical interlocking, and physicochemical interactions on the transfer of shear stresses at

the fiber-matrix interface.

Figure 2. Fiber break patterns from E-glass/DGEBA/

m-PDA 2-D multi-fiber array (stressed). The interfiber

spacing is denoted by φ.
 Multiphase Polymeric Materials 

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Most polymer blends exhibit a phase

separation that leads to a heterogeneous morphology. The scale and

type of the morphology determines

the properties of the polymer blend.

However, understanding the relation

between the morphology and the

properties of polymer blends is still

lacking. In order to explore this relation, we performed computational

studies that combine simulation of

phase separation with generic finite

element approach through a computer

program having the capability of

morphology adaptation. This combination of modeling can help to identify the potentials of

multiphase material behavior and can serve as a virtual

experimental tool. This tool allows scientists to explore

behavior on the scale of the microstructure and to compare that behavior with macroscopic properties. Consequently, it can result in reduced material fabrication costs

and improved material performance. Currently, our study

has been limited to binary polymer blends.

Poly-OOF: A Virtual

Experimental Tool for

Polymer Research

The understanding of the relation between the morphology and properties of a polymer mixture is still lacking.

Our objective is to develop a morphology-adaptive approach that allows scientists and engineers to explore

the behavior on the scale of the microstructure and compare that behavior to macroscopic properties.

Martin Y.M. Chiang, Charles C. Han

The procedure of the virtual experiment is illustrated in

Figure 1. The phase separation of polymer blends is simulated using a Cahn-Hilliard-Cook model solved with a finite

difference scheme. The micrograph of the simulated morphology is automatically adapted through NIST-developed OOF (Object-Oriented Finite Element Program),

which converts the information describing the microstructure into a finite element mesh (Figure 2). The resulting

mesh is used by a general-purpose finite element program

(Abaqus) to formulate a mathematical model of the physical system subjected to virtual external influences. The

material properties of the blends can then be calculated

and the response visualized to explore the interaction of

the components. To date, the elastic modulus and coefficient of thermal expansion have been predicted for a range

of simulated microstructures of a phase-separated binary

system. Three combinations of material models have been

considered that correspond to glassy-glassy, rubberyrubbery, and glassy-rubbery states of the components of

the system.

M.Y.M. Chiang, N. Parekh, S. Glotzer, J. He, C.C. Han (Polymers Division, NIST)

Center for Theoretical and Computational Material Science, NIST

Figure 1. Flow chart of the proposed FEA as a virtual

experimental tool.

Figure 2. Micrograph of simulated morphology and finite

element mesh.

Cahn-HilliardCook Model to 

Predict Phase 

Separation

Preprocessor

of OOF

(ppm2oof)

Create

ABAQUS

Input File

(oof2abaqus)

ABAQUS

Preprocessor

(Finalization)

Mathematical Model of Physical 

Systems Subjected to Virtual

External Influences

Visualize the Response and 

Predict Physical Properties

ABAQUS

Preprocessor

(Finalization)

Mathematical Model of Physical 

Systems Subjected to Virtual

External Influences

Visualize the Response and 

Predict Physical Properties

Prediction of 

Properties

(Finite Element)

Prediction of Phase 

Separation

(Finite Difference)

OOF Prediction of 

Properties

(Finite Element)

Prediction of Phase 

Separation

(Finite Difference)

OOF
44

Polymer Characterization

The Polymer Characterization Program provides measurement methods, data, and Standard Reference Materials

(SRMs) needed by U.S. industry, research laboratories, and

other federal agencies to characterize rheological and mechanical properties of polymers, their processibility and

performance, and to improve process control. In response

to the critical needs of industry for in-situ measurement

methodologies, a substantial effort is under way to develop

optical, dielectric and ultrasonic probes for use in extrusion

and injection molding. Improved methods for determining

molecular mass distribution of polymers are developed

owing to the dramatic effect it has on processibility and

properties. Mechanical properties and performance are

significantly affected by the solid-state structure formed

during processing. Importantly, unlike many other common

engineering materials, polymers exhibit mechanical properties with time dependent viscoelastic behaviors. As a result, the program also focuses on techniques that measure

the solid-state structure and rheological behavior of polymeric materials.

Chromatographic techniques, which require calibration by

standards of known molecular mass, are the principal methods for determining molecular mass distribution. Because

calibration standards are lacking for most polymers, crude

approximations must be used to interpret chromatographic

data. Recent program activities exploit advances in mass

spectrometry using matrix-assisted laser desorption ionization to develop the method as a primary tool for the determination of the molecular masses of synthetic polymers,

with particular emphasis on commercially important

polyolefins. Advances are sought in measurements of the

solid-state structure of polymers, including optical coherent tomography, inelastic neutron scattering, and sum

frequency generation spectroscopy.

The extrusion visualization facility combines in-line microscopy and light scattering for the study of polymer blends,

extrusion instabilities, and the action of additives. Current

research focuses on understanding and controlling the

“sharkskin instability” in polymer extrusion. Fluorescence

techniques are developed to measure critical process parameters, such as polymer temperature and orientation that

were hitherto inaccessible. These measurements are

carried out in close collaboration with interested industrial

partners.

The polymer industry and standards organizations assist in

the identification of current needs for SRMs. Based on

these needs, research on characterization methods and

measurements are conducted leading to the certification of

SRMs. Molecular standards are used primarily for calibration of gel permeation chromatographs, the principal

method employed by industry for assessing molecular

mass and molecular mass distributions. Melt flow standards are used in the calibration of instruments used to

determine processing conditions for thermoplastics. NonNewtonian rheological standards are also developed to

exhibit the typical polymeric behaviors of shear thinning

and normal stresses; these standards are also used for

calibration of rheological instruments and for research into

improved measurement methods. Reference biomaterials

are produced for test method harmonization, assessment of

new materials, and generation of reference data.

Contact Information: Bruno M. Fanconi
 Polymer Characterization 

Contributors

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Collaborators:

45

Optical coherence tomography (OCT) is a non-invasive,

non-contact optical imaging technique that allows the

visualization of microstructure within bulk materials. OCT

uses a near-infrared low coherence source and a scanning

fiber optic interferometer for depth discrimination. Reflections generated from material heterogeneity are collected as

a function of depth. A requirement for this type of tomography is that the material be transparent to near infrared light,

Optical Coherence

Tomography

We have adapted optical coherence tomography (OCT),

a new method for medical imaging, to the realm of material science. More specifically, we apply OCT for mesoscale, volumetric characterization of polymer composites,

birefringence, polymer blends, biomaterials and ceramic

coatings that cannot be obtained by any other technique.

A volumetric representation of the internal structure of

the above materials in the micrometer- to millimeter-size

scale is often required to understand how various properties of interest are interrelated.

polarization sensitive (PS-OCT) and these systems gather

information about sample birefringence.

OCT has been used historically for medical imaging. We are

bridging the gap between materials science and medicine by

using OCT to non-destructively elucidate the meso-scale

structure of heterogeneous polymeric systems, including

biomaterials and polymeric composites. An advantage of

OCT is the ability to image biomaterials, such as tissue engineering products, in aqueous medium to mimic their natural

state. Critical characterization challenges in tissue engineering scaffolds are to quantify pore size, size distribution and

tortuosity and to relate these variables to some measure of

the success of cell growth. By generating scaffolds with

systematic variations in pore size and pore connectivity, cell

growth can be studied quantitatively. In this work, samples

made of polycaprolactone and poly(ethylene oxide), PEO,

blends were annealed to various times at 75 °C. Then, the

PEO phase was removed by dissolving in water. Pore size

distribution and tortuosity of these materials were obtained

successfully from OCT results. Given the success of this

initial work, the next phase of this project will consist of

relating the cell growth to the 3-D pore structure of scaffolds

generated with systematically varying microstructure.

Two issues in the area of composites were addressed using

OCT. Reinforcement microstructure affects the success of a

composite part during the manufacturing process. OCT was

used to image the reinforcement microstructure and thereby

provide insight into the flow characteristics of the resin

inside the mold. Secondly, OCT was used to identify various

damage modes within a glass-reinforced composite. An

example is given in the figure where the breaks along the

glass fiber are marked by the arrows. The birefringence in

the polymer matrix surrounding the breaks is responsible

for the optical contrast. In the near future our OCT system

will be upgraded to include a polarization sensitive capability. Effort will be directed to quantify birefringence in 3-D. In

addition, data dropout from sample birefringence will be

compensated for, to provide an increased image

depth in deformed samples.

making many polymer systems excellent candidates. The

imaging is performed by collecting back-reflected light

generated from heterogeneities within the sample. The

higher the refractive index mismatch at a boundary, the

stronger the return reflection at any given depth. Thus,

OCT has the ability to distinguish different types of features. OCT is attractive because of its high sensitivity,

which enables a typical sample to be imaged at depths

anywhere from 0.5 mm to 4 mm. The resolution of the system is 10 μm to 20 μm. Recently, resolutions of 3 μm have

been reached with state-of-the-art lasers, electronics and

optics. Additionally, OCT systems have been built that are

G.A. Holmes, W.G. McDonough, M.Y. Chiang, N.R. Washburn, A. Karim (Polymers

Division, NIST)

T. Griffin (Information Technology Laboratory, NIST)

An OCT image of the multiple breaks of a glass fiber

embedded in polymer matrix. The breaks in the fiber

become visible in OCT through the stress-induced birefringence of the matrix material. The locations of the

breaks are marked by arrows in the figure.

Joy P. Dunkers
Polymer Characterization

Contributors

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Collaborators:

46

New methods of traditional metal cationization on fully

saturated polyethylenes are explored in collaboration with

Professor Liang Li of the University of Alberta. In this work,

silver is used as the metal cation as is typical for synthetic

polymer mass spectrometry; however, instead of using the

usual organic acid matrices finely divided cobalt powder is

substituted. Mass spectra of intact oligomers up to 5000 u

have been measured, indicating intact parent in cationization by silver is possible; however, fragmentation ions are

always present complicating spectral interpretation. It is

well-known that most metal ions will insert into C-C bonds

leading to fragmentation on the time scale of the experiment.

A chemical modification method has been developed in the

Polymers Division that allows mass spectrometry to be

performed on saturated hydrocarbon polymers. Two synthetic steps are involved: selective bromination of the polymer, followed by conversion of the brominated site to a

charged ammonium or phosphonium group. A strong mass

spectrum was produced from the modified polymers while

the unmodified and the brominated polymers produced no

signal at all. This concept has been termed the “covalent

cationization method” and has also been demonstrated on

unsaturated olefins such as polystyrene and polybutadiene.

It is envisioned that this method may become applicable to

all types of polymers complementing, or possibly replacing,

the metal cationization methods already in use.

Physical ionization methods are also considered. Removal

of valence electrons by electron or photon irradiation typically results in excess energy imparting to the molecule and

subsequent scission of the C-C bonds. This leads to an

abundance of fragment ions. Working with Daniel Fischer

(Ceramics Division) using the NIST vacuum-ultraviolet

beamline U7A at the National Synchrotron Light Source at

Brookhaven National Laboratory (Upton, N.Y.) carbon core

electrons were ejected from gas-phase alkanes. The photon

energy can be tuned to promote Auger relaxations from the

C-H bonds and not from the C-C bonds to avoid chain

fragmentation. Figure 1 shows a comparison of core-level

photoionization and electron-impact ionization for propane.

Polyolefin Mass

Spectrometry

William E. Wallace

Saturated hydrocarbon polymers, polyethylene and

polypropylene, are the most widely used of all synthetic

polymers. Their molecular-mass distribution (MMD) is

critical in determining performance properties.Mass spectrometry is currently the most promising method for obtaining accurate, absolute MMDs; however, polyethylene

and other polyolefins have not been amenable to mass

spectrometric characterization due to the ineffectiveness

of conventional methods of cationization. The Polymers

Division has addressed this challenge with three distinct

cationization approaches: traditional metal cationization, chemical modification, and physical ionization.

The photoionization does bias the mass spectrum toward

proton loss compared to the electron-impact ionization;

however, residual vibrational energy in the room temperature propane combined with overlap in the valenceelectron orbitals leads to not insignificant C-C bond

scission.

W.E. Wallace, C.M. Guttman, B.M. Fanconi, B.J. Bauer, S. Lin-Gibson, L. Brunner,

D.L. Vanderhart, W.L. Wu, W.R. Blair (Polymers Division, NIST)

D.A. Fischer (Ceramics Division, NIST)

L. Li, T. Yalcin, R. Chen (University of Alberta)

Figure 1. Comparison of core-level photoionization with

287.5 eV photons ( C 1s → C-H σ* transition) and

electron-impact ionization with 70 eV electrons for propane. The parent ion at 44 u is seen in both spectra. The

core-level photoionization is dominated by ions at 38 u to

40 u created by the loss of hydrogen atoms while the

electron-impact ionization is dominated by C-C bond

cleavage as evident from a major peak at 29 u corresponding to C2

H5

+

.

Industry Interaction:

Discussion of measurement needs and future collaborations on polyolefins with Dow Chemical, ExxonMobile,

and Union Carbide is in progress.
 Polymer Characterization 

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47

Fluorescent sub-micrometer probe molecules are needed to

characterize structures and transport properties of membranes, polymer blends and biomaterials. An ideal fluorescent probe would exhibit monodisperse size, versatile solubility, high luminescence, minimal photobleaching, and

stability under conditions of varying temperature, solvent

and pH. Taken together, these criteria are rather demanding

making the development of model probes a challenge.

With the goal of fluorescent probes in

mind, we prepared and characterized a

new class of highly branched, starshaped polymers containing fluorescent tags. These stars have welldefined structures with effective solution-phase diameters on the order of

10–100 nm (0.01–0.1μm). The stars can

be tagged with either an organic

fluorophore or with fluorescent semiconductor nanocrystals (“quantum

dots”). The attractive features of these

novel probes include controllable

polymer architecture and tunable

photophysical properties.

number of arms contain unreacted primary amine endgroups, which function as reactive sites for the attachment

of organic dyes. The labeled stars are highly luminescent

and color-tunable, but organic fluorophores often exhibit

poor resistance to photobleaching.

Semiconductor nanocrystals, such as CdS or CdSe, are an

alternative type of photobleach-resistant fluorescent

marker. PAMAM dendrimers interact

strongly with many types of metal

ions, including Cd2+, allowing attachment of CdS nano-crystals to the

star polymer cores. We have prepared successfully highly fluorescent star-CdS nanocomposites and

characterized their physical properties. Gel permeation chromatography

and small-angle neutron scattering

experiments indicate that the CdS

nanocrystals may be introduced

without disturbing the size distribution of the stars. Although it has not

been straightforward to achieve

color tunability, these materials are a

Fluorescent

Sub-Micrometer Probe

Molecules with Starlike

Architecture

Ronald C. Hedden, Barry J. Bauer

Rapid advances in nanostructured materials technology

motivate development of new methods for stuctural characterization. We are developing fluorescent polymeric

markers for use as probes of sub-micrometer features in

membranes, polymer blends and biomaterials. Fluorescent star-shaped polymers with effective sizes in the

10–100 nm range have been targeted as model probes.

The detection of fluorescent probes using advanced

optical techniques could lead to new methods in polymer

structural characterization.

R.C. Hedden, B.J. Bauer (Polymers Division, NIST)

C. Muzny (Chemical Sciences and Technology Laboratory, NIST, Boulder)

F. Gröhn (Max-Planck-Institut für Polymerforschung, Mainz, Germany)

Figure 1. Schematic diagram of a novel

fluorescent probe: dendrimer-star polymer containing a CdS nanocrystal.

Stars are prepared by attachment of

monofunctional poly(ethylene glycol)

(PEG) “arms” to poly(amidoamine)

(PAMAM) dendrimer “cores”.

Dendrimers are layered, treelike polymers that contain

many functional endgroups. The number of dendrimer

endgroups increases geometrically with the dendrimer

“generation,” or number of layers. The maximum number

of PEG arms that may be attached is equal to the number

of dendrimer endgroups. A PAMAM Generation 4 star

may have up to 64 arms, and a PAMAM Generation 7 star

may have up to 512, for example. PEG was chosen for the

“arms” due to its versatile miscibility with water, organic

solvents and many polymers.

Using a standard synthesis, we have labeled the stars with

organic fluorophores. Stars with less than the maximum

milestone in the development of

photobleach-resistant fluorescent

probes.

Current work focuses on testing

fluorescent star polymers as probes. Researchers at NIST

(Boulder) are characterizing mass transport in membranes

by novel combinatorial methods using fluorescent probes.

To facilitate this study, we are developing a series of fluorescent stars with well-defined sizes and independent

emission spectra. We are also interested in observing the

behavior of the stars in immiscible polymer blends using

advanced optical microscopy techniques. We will determine whether the stars migrate to phase boundaries to

help explain how highly branched polymers affect the

properties of immiscible blends.
Polymer Characterization

Contributors

and

Collaborators:

48

Standard Reference Materials and Reference Materials are

issued to address needs of the producers, processors and

users of polymers for calibration and for performance

evaluation of instruments used in the control of the synthesis and processing of polymers, as well as benchmarks

for comparisons of measurement methods and development of new materials. Recently produced Standard Reference Materials include polyethylene of narrow mass distribution certified for mass average molecular mass and

intrinsic viscosity and a nonlinear fluid standard for rheological measurements. In addition, the first reference biomaterial, RM 8456, an orthopedic grade ultra-high molecular weight polyethylene, UHMWPE, was issued for use in

development of improved test methods for wear and as a

benchmark for development of improved materials. Radiation cross-linking of UHMWPE is being pursued by the

orthopedics products industry for improved wear resistance products. Better test methods for degree of crosslinking are under evaluation by ASTM through

interlaboratory comparison on irradiated samples produced from RM 8456. NIST participated by providing

specimens of RM 8456 in a form suitable for the

interlaboratory comparison. In anticipation of continuing

need for Reference Material UHMWPE for radiation studies NIST is issuing orthopedic grade UHMWPE cubes for

radiation cross-linking tests and analysis. This Reference

Material is produced from RM 8456.

Among polymer standards provided by NIST are those

certified for melt flow, the primary characteristic of a polymer melt used by both producers and processors of polymers to determine the required characteristics of processing equipment. The NIST melt flow standards are

referenced in ASTM test method for melt flow for use in

assessing laboratory proficiency. Stock of SRM 1473, a

melt flow standard, will be depleted in a few months. To

address the continuing need for this standard a new batch

of resin, from the same source as that used to produce

SRM 1473, is certified for melt flow. Current standard test

method for melt flow extends to temperatures and flow

Standard Reference

Materials

Charles M. Guttman, Carl R. Schultheisz

Reference Materials (RM) and Standard Reference Materials (SRM) are produced to address needs of the producers, processors and users of synthetic polymers for calibration of instruments, assessment of laboratory proficiency,

test method development and materials development. An

orthopedic grade ultra-high molecular weight polyethylene RM is prepared in the form of cubes for irradiation

studies. Recertification of a melt flow standard and certification of a non-Newtonian fluid for rheological properties

assist polymer processors and producers. The first polymer

molecular mass standard is produced with the complete

mass spectrum as ancillary data.

rates under which polymer melts typically degrade,

thereby affecting the reliability of the result. Test conditions are determined under which a thermally stabilized

resin would have sufficient stability to render melt flow

measurements more meaningful. A high temperature, high

flow rate melt flow standard would be used for performance evaluation under these conditions.

SRM 2490, a non-Newtonian polymer solution for rheological measurements, was issued for use in calibration

and performance evaluation of instruments used to determine viscosity and first normal stress difference in steady

shear, or to determine the dynamic mechanical storage and

loss moduli and shift factors through time-temperature

superposition. Discussions with potential customers of

SRM 2490 revealed the need for a second non-Newtonian

fluid designed for calibration and performance evaluation

of rheometers that lack the stringent temperature control

required for calibration with SRM 2490. A suitable polymer

fluid, poly (dimethylsiloxane), has been procured to meet

these requirements. We will conduct homogeneity measurements followed by certification for non-Newtonian

viscosity and the first normal stress difference over a

range of temperatures and shear.

SRM 2888, polystyrene possessing a narrow molecular

mass distribution, is certified for mass average molecular

mass by light scattering. The number average molecular

mass determined by high-resolution NMR and mass spectrum measured by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) are provided as

ancillary data. This material was used in an interlaboratory

comparison of mass distribution measurement by MALDI

MS. The results of the analysis of data submitted by the

18 participating laboratories were published in the journal

Analytical Chemistry (Anal. Chem. 2001, 73 1252-1262).

Additional information on the interlaboratory comparison

is given in the accomplishment section of this report

under the title “Polymer Mass Distribution by Mass

Spectrometry.”

C.M. Guttman, C.R. Schultheisz, J.A. Tesk, W.R. Blair, D.L.VanderHart, B.M. Fanconi,

W.E. Wallace, S.J. Wetzel, R. Goldschmidt (Polymers Division, NIST)

Interlaboratory Comparison, Industrial Participants: Lab Connections, Eastman

Chemicals, Air Products, 3M, ICI, Charles Evans & Associates, Hercules, Bruker

Daltonics, Zeneca, Union Carbide, DuPont
 Polymer Characterization 

Contributors

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49

Sample Preparation

For synthetic polymers samples, MALDI TOF MS can yield

quantitative information about end groups, repeat units,

molecular masses and molecular mass distributions. Accurate quantitative measurements require equimolar responses for all sample species in the mass range over

which a sample is distributed.

Efforts to modify MALDI sample preparation techniques

for synthetic polymers with the goal of increasing sample

homogeneity and the equimolar peak signal intensity have

met with modest success. The usual sample preparation

method involves hand-depositing on the sample plate. This

sample preparation technique leads to variations in MALDI

signal intensity as the ablating laser beam scans across the

sample, indicating sample inhomogeneities on the size of

the laser spot (25 μm). An electrospray sample preparation

technique showed improvement in the statistical variation

of MALDI intensities as long as the sprayed coating was

thick.

Experiments were conducted also to address sample morphology in the nanometer scale with the goal of determining if optimal MALDI signal was obtained when analyte

molecules were molecularly dispersed in the matrix. This

question derives from the premise that the lack of MALDI

signals from polyolefins may relate to their segregation

from the matrix owing to rapid crystallization under the

sample preparation conditions used. Small-angle neutron

scattering has been used to measure the size and level of

dispersion of synthetic polymers in MALDI samples prepared by electrospraying. In dithranol, a common matrix,

deuterated polystyrene (PSD) was found by SANS to form

aggregates of size greater than 20 nm. The size of the aggregates appears to be unaffected by the solution concentration of PSD in sample preparation, at least over the concentration range typically used. This suggests that

reproducible MALDI results may be obtained without

molecularly dispersed polymers.

Quantitative Mass

Spectrometry of

Synthetic Polymers

Charles M. Guttman

The molecular mass distribution (MMD) of a polymer has

profound effects on how it is processed and the resultant

properties. Recent advances in matrix-assisted laser

desorption/ionization (MALDI) time-of-flight (TOF) mass

spectrometry (MS) suggest that it is possible to obtain

the MMD of undegraded polymer molecules with molecular masses up to 300,000 g/mol. Experiments in this

project are directed to the use of MALDI to obtain the

measurement of the absolute molecular mass distribution

of synthetic polymers.

More definitive results were obtained on a new type of

matrix for MALDI, tri-α-naphyl benzene, that forms both

glass and crystalline states. By SANS it was shown that

PSD is molecularly dispersed in the glass, but segregated in

the crystalline state. Figure 1 below shows that the MALDI

signal is inferior when PSD is dispersed molecularly in the

glass compared to the MALDI signal obtained when PSD is

phase separated.

C.M. Guttman, B.J Bauer, W.R. Blair, W.E. Wallace, R. Goldschmidt, S.J. Wetzel,

A.P. Weaver (Polymers Division, NIST)

Baselines in Data Analysis

To derive quantitative results from MALDI spectra care

must be given to treatment of the baseline, particularly in

spectra where the signal does not return to the same minimum value between each oligomeric peak. A common feature in the MALDI spectrum of synthetic polymers is the

appearance of a broad featureless hump that underlies the

spectral data. The broad hump is usually offset to the

higher mass side with respect to the envelope of the peak

distribution and it may extend beyond the highest mass

identifiable oligomeric peak. Including the hump as part

of the polymer signal in the analysis can affect significantly

derived moments of the distribution (for comparisons with

other methods, for example). In a set of definitive experiments it was shown that the broad hump results from fragmentation products and polymer-matrix adducts. For this

reason the proper treatment is to eliminate the broad hump

from spectral data to obtain the MMD and its moments.
Polymer Characterization

Contributors

and

Collaborators:

50

Approximately $140 billion are spent annually on health

care measurements associated with biomedical devices,

quality control and many other diagnostic and therapeutic

procedures. NIST workshops have identified needs for

reference biomaterials (RBMs, 1998) and reference biomaterial properties data (RBMPD, 2000). Among these were

reference bars of medical grade Ultrahigh Molecular Mass

(weight) Polyethylene (UHMWPE). NIST has responded

by stocking a supply of UHMWPE RM 8456 which became available in October 2000. At the 2000 RBMPD workshop, participants identified a major need for a national

biomaterials properties database system. Properties of the

database system include portals with data from different

sources, one with data as supplied by manufacturers of

biomaterials and biomedical devices, another with data

from testing laboratories such as those of the FDA, and a

NIST database with data from the literature and from certificates that accompany NIST Reference Materials (RMs)

and Standard Reference Materials of biomaterials. A property of the NIST database is that it contains critical evaluations of the properties included. Certificate data for reference biomaterials was seen as an important source for

critically reviewed properties database. An alliance was

formed with several intraocular lens and biomaterial companies, and two major university eye clinical centers for

the development of intraocular lens reference materials

and reference data. Alliances are being pursued for a

tissue engineered products reference scaffold and for the

development of additional orthopedic reference materials.

Support for the

Biomaterials Integrated

Products Industries

John Tesk

NIST workshops have established the needs of the medical

devices industry (BIPIs) for reference materials, test methods, and reference data. In this project a continual assessment is made of the technical needs of BIPIs to inform NIST

management for program planning. Leadership is taken to

help form alliances, within and outside of NIST, to respond

to those needs. Needs are explored through participation

on numerous standards boards and their committees, on

committees/boards of professional societies and academic

institutions, and via liaisons with NIH, FDA, the American

Academy of Orthopaedic Surgeons, and the American

Dental Association.

Participation and leadership in standards organizations are

seen as other means for assessing the needs for other

RMs and RBMPD. Collaboration continues with industry

and an ASTM committee for the development and supply

of UHMWPE reference cubes that can be used for swelling measurements for the determination of crosslink density as a result of ionizing radiation (crosslinking affects

wear resistance and durability of orthopedic joint implant

bearing surfaces).

A workshop on Standards for Biomedical Materials and

Devices was identified by NIST major operating units at a

meeting convened by the Materials Science and Engineering Laboratory, as a means for establishment of a NISTwide strategy for work on standards in support of the

biomedical devices industry. The Polymers Division held a

major role in the organization and operation of the workshop, which was held on June 13, 2001. The workshop

identified action items for NIST early follow-up in support

of the biomedical materials and devices industry, and items

for consideration of future NIST responses to the

industry’s needs for standards.

Publications were also pursued to provide greater visibility of NIST to the BIPIs community. An invited paper on

the proceedings of the RBMPD workshop was published

in the July issue of the Journal of Biomedical Materials

Research, Applied Biomaterials.

J.A. Tesk, B.M. Fanconi (Polymers Division, NIST)

C. Croarkin (Statistical Engineering Division, NIST)

J. Sheets (Alcon Research), K. White (Polymer Technology Group), F. Eichmiller

(American Dental Association Paffenbarger Research Center, NIST), J. Jacob (LSU

Eye Center), S. Spiegelberg (Cambridge Polymer Technology), S. Kurtz (Exponent

Inc.), B. Liebler, J. Benson (AdvaMed)
 Polymer Characterization 

Contributors

and

Collaborators:

51

The understanding and control

of extrusion instabilities is hampered by the lack of experimental

techniques that provide realtime data at sufficient spatial

and time scales. We recently

have upgraded the Extrusion

Visualization Facility so that it

can operate at high-speed/high

magnification. Using our new

capabilities, we collected an

abundance of data that clarifies

several of the uncertainties

regarding the nature of the sharkskin instability (see accomplishment report). Buoyed by that success, we are opening

efforts to study the “gross melt fracture instability”, to

develop new metrology to quantitate the polymer processing additive coating process, and to probe the correlation

between instabilities and molecular architecture.

Sharkskin and Gross Melt Fracture

Using the extrusion visualization facility, we examine the

flow behavior of the polymer as it is extruded through a

capillary rod. High-speed microscopy of the material as it

exits the tube reveals that the molten material tears at its

surface just at the exit from the tube. The central core of the

material extrudes at high speed while the surface region

tears, peels off and then joins the central core (see Figure).

Current work is examining an extrusion instability known as

gross melt fracture. This is characterized by severe distortions in the extruded material. Traditionally, it is believed

that this instability occurs in the region where the material

narrows down from a large diameter to a small one, well

upstream of the capillary exit. However, we recently have

discovered that the exit region may be of importance. We

have discovered that the material undergoes transientspontaneous cavitation in the exit region of the tube during

gross melt fracture. We intend to understand cavitation and

its implications for gross melt fracture control.

Control of Extrusion

Instabilities

Kalman B. Migler

Polymeric materials have become ubiquitous in the modern economy because they are comparatively easy to

process. However, polymeric materials exhibit complex

and sometimes catastrophic responses to the forces imposed on them during manufacturing. These instabilities

limit the rates at which the materials can be processed. In

this project we seek new measurement technologies to

understand and control processing instabilities.

Measurement of In-situ Coating

Process

Polymer Processing Aids (often

fluorocopolymers) eliminate sharkskin

by reducing the extensional deformation of the polymer as it exits the die.

In order to work, the fluoro-copolymer must first coat the die’s internal

surface. This coating process is critical to product performance, yet there

are no in-situ quantitative measures

of the coating. Here, we seek a new

measurement technique for the coating of a fluoropolymer additive based on evanescent wave

induced shifts in optical reflection. We propose to measure

quantitatively the formation and growth of the fluoro-polymer layer onto the solid wall through use of total internal

reflection. When the fluoropolymer starts to coat the internal wall, the conditions of total internal reflection will be met

and dramatic changes in optical reflection are predicted. The

thickness of the fluoropolymer layer at which this technique

first becomes effective is determined by the penetration

depth of the evanescent wave (the exponentially decaying

light that does not become reflected). For the materials used

here, the effects of the wall will be felt when its thickness is

approximately 100 nm, which is exceptional for an optical

measurement.

Molecular Architecture and Extrusion Instabilities

One of the great challenges in rheology is to elucidate the

connection between molecular architecture and rheology,

and to apply this knowledge to the study of flow instabilities. This question is particularly important because recent

synthetic strategies allow for precise control of the molecular architecture, such as long chain branching and molecular

mass distribution. We are starting a project to use and develop our measurement tools to examine critical flow parameters at the onset of various extrusion instabilities. We will

correlate these measurements with characterized materials

that have systematic variations in architecture.

K.B. Migler, P.M. McGuiggan, Y. Son (Polymers Division, NIST)

3M Canada Co., 3M Company, Dyneon LLC, Dow, MMI
Polymer Characterization

Contributors

and

Collaborators:

52

Optical Technique

Over the past several years we have concentrated our

attention on the development and use of optical techniques

involving light transmission and fluorescent molecular

probes. We have instrumented extrusion and injection

molding machines and shown how optical sensors can

provide a wealth of information about the resin under processing conditions. When selected fluorescent probe molecules are added to the resin, we can use them to monitor

resin temperature and molecular orientation. The fluorescent probes are mixed with the resin at very low concentrations, less than 10-5 mass fraction of dye in the resin.

A class of fluorescence molecules

called band definition dyes is used

to measure temperature. We have

discovered several dyes that survive processing temperatures up

to 300 oC. They are benzoxazolyl

stilbene (BOS), perylene, and

bis(di-tert-butylphenyl)-perylene

dicarboximide (BTBP). These dyes

display their fluorescence in distinct spectral bands that have

individual temperature dependence. The basis for measuring

temperature is the temperature

dependence of the shape of the fluorescence spectrum.

The fluorescence temperature measurement method is used in collaborative programs with three industrial

R&D laboratories—Exxon/Mobil

Films, DOW Chemical, and Data-point

Labs. At Exxon/Mobil we are monitoring the temperature of biaxially

stretched polypropylene films that

contain the fluorescent dye BTBP.

Real-Time Process

Monitoring

Real-time, on-line measurements of resin materials properties are desirable not only because they preempt the

need for post processing characterization but also because they can be used to monitor resin conditions, to

detect problems with processing parameters and to control the process. In this project, we are developing measurement techniques based on optical, dielectrics, and

ultrasonics techniques. The work involves the design and

construction of sensors and the application of these

sensors to real-time process monitoring.

The temperature measurement is obtained from the BTBP

fluorescence spectrum by measuring the ratio of intensities

at 544 nm and 577 nm. The biaxial stretching must be carried

out between 155 o

C and 162 oC. Typical steady-state monitoring is shown in the upper figure. The standard uncertainty for the temperature measurements is 2 o

C.

Dielectric Measurements

In collaboration with Chemical ElectroPhysics Corp. (CEP),

we have carried out in-line dielectric measurements during

extrusion of filled polymers. CEP’s in-line dielectric cell has

a ring design with the inner surface of the ring containing

interdigitated electrodes. The cell is contained in a temperature control housing and is

attached to the exit of an extruder. By applying a small

voltage to the electrodes, a

fringing field intercepts the

resin flowing through the ring.

Associated circuitry in conjunction with calibration of the

instrument yields measurements of permittivity and conductivity. Real-time measurements of filled polymers are

used to monitor filler concentration, transition times between resin loadings, and the

dielectric properties of the melt.

Consider the data shown at left

for processing of polystyrene

filled with aluminum oxide. The

data are a plot of relative permittivity versus time for processing of polystyrene filled

with 20 percent by mass aluminum oxide powder. The uncertainty in permittivity measurements is 0.01.

Anthony J. Bur

A.J. Bur, S.C. Roth (Polymers Division, NIST)

Exxon/Mobil Films, Dow, Data-point Labs, Chemical ElectroPhysics Corporation
 Polymer Characterization 

Contributors

and

Collaborators:

53

Micro-scale Processing

Kalman B. Migler

Micro-scale processing is an emerging technology with

applications in the optical, medical, and “lab-on-chip”

industries. However, many concepts developed for macroscopic processing break down in this regime. The goal of

this work is to advance the technology infrastructure to

support the growth of these industries.

K.B. Migler, J. Pathak, Y. Son (Polymers Division, NIST)

N. Martys (Building and Fire Research Laboratory, NIST)

J.E. Devaney (Information Technology Laboratory, NIST)

We are exploring the

effects of confinement

and the breakdown of

mixing that occur in

the micro-scale regime.

The two sub-projects

described below are

designed to bring the

synergistic advantages brought by

polymer blending into

the fabrication of

small-scale structures.

Confinement and

Stability of Liquid

Threads

It has been known

since the 19th century

that a liquid thread immersed in a fluid is unstable—it

breaks into a sequence of droplets. Recently we have

shown that it is possible to stabilize the thread by confining it between two parallel walls. This result is important in

emerging micro-fluids technology as well as in microinjection molding. By combining experiments, interfacial

area calculations, and Lattice-Boltzman numerical simulations (See Figure), we systematically explore the relevant

parameter space. The emerging confluence between the

experimental and numerical results will allow us to model

and optimize the behavior in complex geometries before

building actual devices.

Further application of this work has led to the development of an improved method for the measurement of interfacial tension that combines the advantages of existing

techniques while eliminating their disadvantages. We thus

believe that it will become the method of choice for interfacial tension measurements in polymer blends.

String Structures

in Confined Blends

Last year, we reported the unexpected discovery of

string formation in

sheared polymer

blends that occurs

when the droplet

size becomes comparable to the gap

width. Now, we are

exploring the consequences of this

finding and the

range of conditions

over which it is

valid. We find that

string formation is

extremely robust, occurring over a wide range of micro-scale

processing conditions. We have observed it over a wide

range of compositions, with string formation occurring at

volume fractions as low as 5 percent, over a range of viscosity ratios from (0.1 to 10) and over a range of elasticities.

We find that extreme care must be taken to ensure the string

morphology is appropriate to the application. Our work also

points the way to potential uses of the technology, for

example to produce scaffolds in tissue-engineered products.

We also report the discovery of layering transitions that

occur when the shear rate is too high to produce the string

structure. We observe that the droplets organize into one,

two, or three layer systems as they are sheared. These

results further emphasize the profound changes that are

induced by confinement.
54

Publications

Akpalu, Y. A. and Amis, E. J., “The Effect of Polydispersity

on the Evolution of Density Fluctuations to Lamellar

Crystals in Linear Polyethylene”; Journal of Chemical

Physics, 2000 Jul 1; 113(1):392–403.

Amis, E. J. and Fanconi, B. M., “Polymer Division FY2000

Programs and Accomplishments”; NISTIR 6596, 2000.

Antonucci, J. M.; McDonough, W. G.; Schumacher, G. E.,

and Shimada, Y., “A Novel Microshear Bond Test To

Measure Dental Adhesion”; Proc. of the 24th Annual

Meeting of the Adhesion Society; Williamsburg, VA,

2001.

Antonucci, J. M.; Skrtic, D., and Brunworth, R. T.,

“Methacrylate Conversion in Photo-polymerized

Composites Containing Amorphous Calcium

Phosphate Fillers”; Polymer Materials Science &

Engineering; in press.

Baklanov, M. R.; Kondoh, E.; Lin, E. K.; Gidley, D. W.; Lee,

H.-J.; Mogilnikov, K. P., and Sun, J. N., “Comparative

Study of Porous SOG Films with Different NonDestructive Instrumentation”; Proc. of the Intl.

Interconnect Technology Conf.; 2001.

Barnes, K. A.; Douglas, J. F.; Liu, D.-W., and Karim, A.,

“Influence of Nanoparticles and Polymer Branching

on Rewetting of Polymer Films”; Journal of Colloid

and Interface Science; in press.

Bauer, B. J. and Amis, E. J., “Characterization of

Dendritically Branched Polymers by SANS, SAXS,

and TEM”, in Dendritic Polymers, ed.: Tomalia, D. A.

and Frechet, J. M. J.; in press.

Bauer, B. J.; Guttman, C. M.; Blair, W. R., and Liu, D.-W.,

“Tri-alpha-Napthyl Benzene as a Glassy or Crystalline

Matrix for MALDI TOF MS of Synthetic Polymers”;

Proc. of the 49th American Society for Mass

Spectrometry Conf.; Chicago, IL, 2001.

Bauer, B. J.; Lin, E. K.; Lee, H. J.; Wang, H., and Wu, W.-L.,

“Structure and Property Characterization of Low-k

Dielectric Porous Thin Films”; Journal of Electronic

Materials, 2001 Apr; 30(4): 304–308.

—, “Structure and Property Characterization of Low-k

Dielectric Porous Thin Films; Polymer Preprints, 2001;

42(1):263–264.

Bauer, B. J.; Wallace, W. E.; Fanconi, B. M., and Guttman,

C. M., “‘Covalent Cationization Method’ for the

Analysis of Polyethylene by Mass Spectrometry”;

Polymer; in press.

Beers, K. L.; Douglas, J. F.; Amis, E. J., and Karim, A., “A

High Throughput Approach to Crystallization in Thin

Films: Isotactic Polystyrene”; Polymer Preprints, 2001;

42(2).

Bouldin, C. E.; Wallace, W. E.; Lynn, G. W.; Roth, S. C.,

and Wu, W.-L.,“Thermal Expansion Coefficients of

Low-k Dielectric Films from Fourier Analysis of

X-Ray Reflectivity”; Journal of Applied Physics, 2000

Jul 15; 88(2):691–695.

Bubeck, R. A.; Bauer, B. J.; Dvornic, P.; Owen, M. J.;

Reeves, S.; Parkham, P., and Hoffman, L. W., “SmallAngle Neutron Scattering from Metal Ion-Containing

PAMAMOS Dendrimer Networks”; ACS PMSE

Preprints; in press.

Bur, A. J.; Migler, K. B., and Roth, S. C., “Process

Monitoring at the National Institute of Standards and

Technology: Celebrating 100 Years of Measurement

Excellence”; Proc. of the Society of Plastics Engineers

2001 Annual Technical Conference, 2001.

Bur, A. J.; Roth, S. C., and Lobo, H., “Temperature

Monitoring of Capillary Rheometry Using a

Fluorescence Technique”; Proc. of the Society of

Plastics Engineers Annual Technical Meeting, 2001.

Bur, A. J. and Roth, S. S., “Fluorescence Based

Temperature Measurements and Applications to RealTime Polymer Processing”; NISTIR, 2000.

Cantoni, G.; Bonner, R. F.; Malekafzali, A.; Douglas, J. F.;

Amis, E. J.; Karim, A., and Sehgal, A., “Laser Diode

Focal Activation of Polymer for New Uses in

Genomics and Gene Expression Research by

Combination of Laser Capture Microdissection with

Medical Molecular Diagnostics”; Conf. Proc. of the

XIV Congresso della Divisione di Chimica Industriale

della Societa Chimica Italiana; Milan, Italy, 2001.

Chai, H.; Chiang, M. Y. and Schultheisz, C. R., “Effect of

Straining Rate on the Mechanical Behavior of

Adhesive Bonds Under Shear Deformation”; Proc. of

the Adhesion Society Meeting, pp. 303–305;

Williamsburg, VA, Feb 2001.
 Publications 

55

Chen, R.; Yalcin, T.; Wallace, W. E.; Guttman, C. M., and Li,

L.,“Laser Desorption Ionization and MALDI Time-ofFlight Mass Spectrometry for Low Molecular Mass

Polyethylene Analysis”; Journal of the American

Society for Mass Spectrometry; in press.

—, “Laser Desorption Ionization and MALDI Time-ofFlight Mass Spectrometry for Low Molecular Mass

Polyethylene Analysis”; Proc. of the 49th ASMS

Conference on Mass Spectrometry and Allied Topics;

Chicago, IL; in press.

Chiang, C. K.; Popielarz, R., and Sung, L. P., “Dielectric

Properties and Morphology of Ferroelectric CeramicPolymer Composite Films”; Symp. Proc. of Materials

Research Society—Microelectronics and

Microsystems Packaging, 2001.

Chiang, C. K.; Sung, L. P., and Popielarz, R., “Investigation

of Morphology and Interface in Polymer Composite

Thin Films”; Symp. Proc. of Materials Research

Society, 2001.

Crosby, A. J.; Karim, A., and Amis, E. J., “Combinatorial

Investigations of Polymer Adhesion”; Polymer

Preprints; in press.

DeReggi, A. S.; Balizer, E.; Neumann, D. A., and Bateman,

F., “Electrostriction Mechanism in Electron-Irradiated

Ferroelectric Copolymer: A Frequency Response

Model”; Conference on Electrical Insulation and

Dielectric Phenomena, 2000.

Douglas, J. F.; Kent, M. S.; Satija, S. K., and Karim, A.,

“Swelling of Grafted Polymer ‘Brushes’”;

Encyclopedia of Materials: Science and Technology;

in press.

Douglas, J. F.; Zhang, Y.; Ermi, B,. D., and Amis, E. J.,

“Influence of Counterion Valency on the Scattering

Properties of Highly Charged Polyelectrolyte

Solutions”, Journal of Chemical Physics, 2001 Feb;

3299–3313.

Dunkers, J. P.; Holmes, G. A., and McDonough, W. G.,

“Imaging of Multi-fiber, Micro-mechanical Testing

Specimens Using Optical Coherence Tomography”;

Proc. of the 24th Annual Meeting of the Adhesion

Society; Williamsburg, VA, 2001.

Dunkers, J. P.; Lenhart, J. L.; Kueh, S. R.; van Zanten,

J. H.; Advani, S. G., and Parnas, R. S.,“Fiber Optics

Flow and Cure Sensing for Liquid Composite

Molding”; Journal of Optics and Lasers in

Engineering, 2001; 35:91–104.

Dunkers, J. P.; Phelan, F. R.; Flynn, K. M.; Sanders, D. P.,

and Parnas, R. S., “Permeability Prediction from NonDestructive Imaging of Composite Microstructure”;

Society of Plastics Engineers 2001 Annual Technical

Conference Proceedings, 2001.

Dunkers, J. P.; Phelan, F. R.; Sanders, D. S.; Everett, M. J.;

Green, W. H.; Hunston, D. L., and Parnas, R. S., “The

Application of Optical Coherence Tomography in

Problems in Polymer Matrix Composites”; Journal of

Optics and Lasers in Engineering, 2001; 35:135–147.

Dunkers, J. P.; Washburn, N. R.; Simon, C. G.; Karim, A.,

and Amis, E. J., “Non-destructive Characterization of

the Morphology of a Polymer Co-Extruded Scaffold

Using Optical Coherence Tomography”; Proc. of the

2001 Annual Meeting of the Society of Biomaterials,

2001.

Eichmiller, F. C.; Tesk, J. A., and Croarkin, C. M.,

“Mechanical Properties of Ultra High Molecular

Weight Polyethylene NIST Reference Material

#8456”; Proc. of the 2001 Annual Meeting of the

Society of Biomaterials, 2001.

Feresenbet, E. B.; Holmes, G. A., and Raghavan, D., “The

Influence of Silane Coupling Agent Composition on

the Fiber-Matrix Interfacial Shear Strength”; Proc. of

the 24th Annual Meeting of the Adhesion Society;

Williamsburg, VA, 2001.

Ferreiro, V.; Douglas, J. F.; Karim, A., and Amis, E. J.,

“Phase Ordering in Blend Films of Semi-Crystalline

and Amorphous Polymers”; Macromolecular

Symposium, 2001; 167:73–88.

Ferreiro, V.; Schmidt, G.; Han, C. C., and Karim, A.,

“Dispersion and Nucleating Effects of Clay Fillers in

Nanocomposite Polymer Films”; Polymer Preprints,

2001.

Flynn, K. M.; Fanconi, B. M. and Amis, E. J., CD-ROM

Polymer 2000 Publications; NISTIR, 2000.

Fuoco, E.; Gillen, G.; Wijesundara, M. B. J.; Wallace, W. E.,

and Hanley, L., “Surface Analysis Studies of Yield

Enhancements in Secondary Ion Mass Spectrometry

by Polyatomic Projectiles”; Journal of Physical

Chemistry B, 2001; 105:3950.

Gebremichael, Y.; Schroder, T. B.; Starr, F. W., and Glotzer,

S. C., “Spatially Correlated Dynamics in a Simulated

Glass-Forming Polymer Melt: Analysis of Clustering

Phenomena”; Physical Review E; in press.

Glotzer, S. C. and Starr, F. W., “Multiscale Modeling of

Filled and Nanofilled Polymers”; Proc. of Foundations

of Molecular Modeling and Simulation, 2000.
Publications

56

Goldfarb, D. L.; Lin, Q.; Angelopoulos, M.; Soles, C. L.;

Lin, E. K., and Wu, W.-L., “Characterization of Thin

and Ultrathin Polymer and Resist Films”, SPIE

Proceedings; 2001.

Goldschmidt, R. J. and Guttman, C. M., “Investigation of

Two Broad Features Often Observed in MALDI Mass

Spectra of Synthetic Polymers”; Proc. of the 49th

American Society for Mass Spectrometry Conf.;

Chicago, IL, 2001.

Grull, H.; Schreyer, A.; Berk, N. F.; Majkrzak, C. F., and

Han, C. C., “Composition Profiling in a Binary Polymer

Blend Thin Film Using Polarized Neutron

Reflectivity”; Europhysics Letters, 2000 Apr;

50(1):107–112.

Guttman, C. M., “Mass Spectrometry”, in Encyclopedia of

Polymer Science and Technology; in press.

Guttman, C. M.; Blair, W. R., and Wetzel, S. J., “Making

MALDI-TOF-MS an Absolute Method for

Determination of the MMD of Polymers”; Polymer

Preprint, 2001; 42(1), 277–78.

Guttman, C. M.; Wetzel, S. J.; Blair, W. R.; Fanconi, B. M.;

Girard, J. E.; Goldschmidt, R. J.; Wallace, W. E., and

VanderHart, D. L., “National Institute of Standards

and Technology Sponsored Interlaboratory

Comparison of Polystyrene Molecular Mass

Distribution Obtained by Matrix Assisted Laser

Desorption Ionization Time-of-Flight Mass

Spectrometry: Statistical Analysis”; Analytical

Chemistry, 2001; 73:1252–1262.

Han, C. C.; Hobbie, E. K.; Nakatani, A. I., and Kim, S.,

“Critical Temperature Shift and Mixing in Polymer

Blends under Simple Shear Flow”; Journal of the

Physical Society of Japan, Supplement A , 2001;

70:317.

Han, C. C.; Schmidt, G.; Nakatani, A. I., and Butler, P., “A

Small Angle Neutron Scattering Study on Polymer

Clay Solutions”; Polymer Preprints, 2001.

Han, C. C.; Schmidt, G.; Nakatani, A. I., and Karim, A.,

“Characterization of Polymer-Clay Solutions by

Rheology, Flow Birefringence and SANS”; Polymer

Preprint, 2001.

Hayashi, M.; Grull, H.; Esker, A. R.; Weber, M.; Sung, L.;

Satija, S. K.; Han, C. C., and Hashimoto, T., “Neutron

Reflectivity Study of Diblock Formation During

Reactive Blending Processes”; Macromolecules, 2000

Aug 22; 33(17):6485–6494.

Hayashi, M.; Hashimoto, T.; Hasegawa, H.; Takenaka, M.;

Grull, H.; Esker, A. R.; Weber, M.; Satija, S. K.; Han,

C. C., and Nagao, M., “Interface Between a

Polysulfone and Polyamide as Studied by Combined

Neutron Reflectivity and Small-Angle Neutron

Scattering Techniques”; Macromolecules, 2000 Oct

31; 33(22):8375–8387.

He, J.; Chiang, M. Y., and Hunston, D. L., “Assessment of

Sandwich Beam in Three-Point Bending for

Measuring Adhesive Shear Modulus”; Transaction

of the ASME, Journal of Engineering Material and

Technology, 2000.

Holmes, G. A.; Feresenbet, E. B., and Raghavan, D., “The

Effect of Self-Assembled Monolayer Technology on

Fiber-Matrix Adhesion”; Polymer Preprints, 2001;

42(1):296–297.

—, “Using Self-Assembled Monolayer Technology to

Probe the Fiber-Matrix Interface”; Proc. of the 24th

Annual Meeting of the Adhesion Society;

Williamsburg, VA, 2001.

Holmes, G. A. and Ford, K., “Epoxy Clay Hybrid (ECH)

Nanocomposites: Strategies for the Dispersion of

Clay Platelets in Amine-Cured Epoxy Resins”; Proc. of

the 16th Annual Technology Conference on

Composite Materials, 2001.

Holmes, G. A. and Peterson, R. C., “Measuring Interface

Strength in Single Fiber Composites: The Effect of

Stress Concentrations”; Proc. of the Materials

Research Society Annual Mtg., 2000.

Holmes, G. A.; Peterson, R. C.; Hunston, D. L., and

McDonough, W. G., “E-Glass/DGEBA/m-PDA Single

Fiber Composites: Interface Debonding During Fiber

Fracture”; Polymer Composites; in press.

Hu, X. S.; Shin, K.; Rafailovich, M.; Sokolov, J.; Stein, R.;

Chan, Y.; Williams, K.; Wu, W.-L., and Kolb, R.,

“Anomalies in the Optical Index of Refraction of Spun

Cast Polystyrene Thin Films”; High Performance

Polymers, 2000 Dec; 12(4):621–629.

Hunston, D. L., “Load History Dependence of Fracture in

Structural Adhesives”; Adhesives Age; in press.

Hunston, D. L.; Juska, T.; Karbhari, V.; Morgon, R., and

Williams, C., “Gap Analysis for Durability of Fiber

Reinforced Polymer (FRP) Composites in Civil

Infrastructure”; Report from Civil Engineering

Research Foundation, 2001.

Hunston. D. L.; Miyagi, Z.; Schultheisz C. L., and Beirson,

H., “Sandwich Bending Specimens for Characterizing

Adhesive Properties”; Mechanisms of TimeDependent Materials; in press.
 Publications 

57

Jeon, H. S. and Hobbie, E. K., “Erratum: Shear Viscosity of

Phase-Separating Polymer Blends with Viscous

Asymmetry [PRE 63, 061403 (2001)]”; Physical

Review E.

—,“Shear Viscosity of Phase Separating Polymer Blends

with Viscous Asymmetry”; Physical Review E., 2001;

63:1403–1408.

Jeon, H. S.; Nakatani, A. I.; Han, C. C., and Colby, R. H.,

“Melt Rheology of Lower Critical Solution

Temperature Polybutadiene/Polyisoprene Blends”;

Macromolecules, 2000 Dec 26; 33(26):9732–9739.

Jeon, H. S.; Nakatani, A. I.; Hobbie, E. K., and Han, C. C.,

“Phase Inversion of Polybutadiene/Polyisoprene

Blends Under Quiescent and Shear Conditions”;

Langmuir, 2001; 17:3087–3095.

Jiang, Y.; Saxena, A.; Lookman, T., and Douglas, J. F.,

“Influence of Filler Particles and Clusters on Phase

Separation in Binary Polymer Blends”; Journal of the

Materials Research Society; in press.

Josell, D. A.; Wallace, W. E., and Wheeler, D., “Wafer

Level Underfill: Experiments and Modeling, Silicon

Microelectronics Programs at the National Institute of

Standards and Technology”; NISTIR 6731, 2001.

Josell, D. A.; Wallace, W. E.; Warren, J.; Wheeler, D., and

Powell, A. C., “Alignment of Flip-Chip Soldered

Electronic Components: Measured and Calculated

Normal and Laterial Force-Displacement

Relationships”; Journal of Electronics Packaging; in

press.

Karim, A. and Amis, E. J., “Combinatorial Methods at

NIST”; NISTIR, 2001.

Karim, A.; Douglas, J. F.; Barnes, K. A.; Nakatani, A. I.;

Liu, D. W., and Amis, E. J., “Studies of Polymer-filler

Interactions in Filled Systems”; ACS PMSE, 2001.

Karim, A.; Douglas, J. F.; Sung, L. P., and Ermi, B. D.,

“Phase Separation in Ultra Thin Polymer Blend

Films”; in Encyclopedia of Polymer Science and

Technology; in press.

Karim, A.; Smith, A. P.; Douglas, J. F., and Amis, E. J.,

“Characterization of Symmetric Diblock Copolymers

with High-Throughput Techniques”; Polymer

Preprints, 2001; 42(1)283–284.

Kondoh, E.; Baklanov, M.R.; Lin, E.K.; Gidley, D.W. and

Nakashima, A., “Comparative Study of Pore Size of

Low-Dielectric Constant Porous Spin-on-Glass Film

with Different Ways of Non-destructive

Instrumentation”; Japanese Journal of Applied

Physics, 200l; 40: L323–L326.

Kumar, S. K. and Douglas, J. F., “Gelation in Physically

Associating Polymer Solutions”, Physics Review

Letters; in press.

Lee, H. J.; Lin, E. K.; Wang, H.; Wu, W.-L.; Chen, W., and

Deis, T. A., “Correlations Between Structural

Characteristics and Process Conditions of HSQ Based

Porous Low-k Thin Films”; Proc. of the Materials

Research Society Meeting, 2001.

Lee, H. J.; Lin, E. K.; Wang, H.; Wu, W.-L.; Chen, W., and

Deis, T. A., “Characterization of Porous Low-k

Dielectric Thin Films Using X-ray Reflectivity and

Small-angle Neutron Scattering”; Proc. of the Intl.

Interconnect Technology Conf., 2001.

Lee, H. J.; Lin, E. K.; Wu, W.-L.; Fanconi, B. M.; Lan, J. K.;

Cheng, Y. L.; Liou, H. C.; Wang, Y. L.; Feng, M. S., and

Chao, C. G., “Investigation of N2

 Plasma Effects on the

Density Profile of Hydrogen Silsesquioxane Thin

Films”; Proc. of the Materials Research Society

Meeting, 2001.

Lenhart, J. L.; van Zanten, J. H.; Dunkers, J. P., and Parnas,

R. S., “Studying the Buried Interfacial Region with an

Immobilized Fluorescence Probe”; Macromolecules,

2001; 34:2225–2231.

—,“Using a Localized Fluorescent Dye To Probe the Glass/

Resin Interphase”; Polymer Composites; in press.

Lenhart, J. L.; van Zanten, J. H.; Dunkers, J. P.; Parnas,

R. S., and Woerdeman, D. L., “Localizing a Fluorescent

Dye To Probe the Buried Interfacial Chemistry”; Proc.

of the 24th Annual Meeting of the Adhesion Society;

Williamsburg, VA, 2001.

Lin, E. K.; Lee, H. J.; Bauer, B. J.; Wang, H.; Wetzel, J. T.,

and Wu, W.-L., “Structure and Property

Characterization of Low-k Dielectric Porous Thin Films

Determined by X-ray Reflectivity and Small-Angle

Neutron Scattering, in Low Dielectric Constant

Materials for IC Applications, ed.: P.S. Ho, J. Leu and

W. W. Lee: Springer Publishing Inc; in press.

Lin, E. K.; Soles, C. L.; Wu, W.-L.; Satija, S. K.; Lin, Q., and

Angelopoulos, M., “Neutron Reflectivity

Measurements for the Interfacial Characterization of

Polymer Thin Film Photoresists”; Proc. of the 12th Intl.

Conf. on Photopolymers, 2001.

Lin, E. K.; Wu, W.-L.; Lin, Q. H., and Angelopoulos, M.,

“Feature-shape and Line-edge Roughness

Measurement of Deep Sub-micron Lithographic

Structures Using Small-Angle Neutron Scattering”;

Proc. of the SPIE 26th Annual Intl. Conf. on

Microlithography, 2001.
Publications

58

Lomov, S. V.; Huysmans, G.; Luo, Y.; Parnas, R. S.;

Prodromou, A.; Verpoest, I., and Phelan, Jr., F. R.,

“Textile Composites. Modeling Strategies.

Composites A: Applied Science and Manufacturing,

2001; 32(10):1379–1394.

Lynn, G. W.; Dadmun, M. D.; Wu, W.-L.; Lin, E. K., and

Wallace, W. E., “Neutron Reflectivity Studies of the

Interface Between a Small Molecule Liquid Crystal

and a Polymer”; Liquid Crystals; in press.

Majumdar, B. S. and Hunston, D. L., “Continuous Parallel

Fiber Composites: Fracture”; in Encyclopedia of

Materials: Science and Technology; Oxford, England:

Pergamon Press; in press.

Mansfield, M. L.; Douglas, J. F., and Garboczi, E. J.,

“Intrinsic Viscosity and the Electric Polarizability of

Arbitrarily Shaped Objects”; Physical Review E.; in

press.

Martys, N. S. and Douglas J. F., “Critical Properties and

Phase Separation in Lattice Boltzmann Fluid Mixtures;

Physical Review E. 2001; 63(031205):1–15.

McBrearty, M.; Bur, A. J., and Roth, S. C., “In-line

Dielectric Monitoring During Extrusion of Filled

Polymers”; Proc. of the Society of Plastics Engineers

2001 Annual Technical Meeting Conference, 2001.

McDonough, W. G.; Amis, E. J., and Kohn, J., “Critical

Issues in the Characterization of Polymers for Medical

Applications”; NISTIR 6535, 2000.

McDonough, W. G.; Antonucci, J. M., and Dunkers, J. P.,

“Interfacial Shear Strengths of Dental Composites by

the Microbond Test”; Dental Composites; Vol 17/6

492–498.

McDonough, W. G.; Antonucci, J. M.; Schumacher, G. E.,

and Shimada, Y., “A Microshear Test To Measure the

Bond Between Dental Composites and Dental

Substrates”; NISTIR 6535, 2000.

McGuiggan, P. M., “The Boundary Lubrication Properties

of Model Esters”; Tribology Letters; in press.

Meredith, J. C.; Smith, A. P.; Karim, A., and Amis, E. J.,

“Combinatorial Materials Science for Polymer ThinFilm Dewetting”; Macromolecules, 2000 Dec 26;

33(26):9747–9756.

Meredith, J. C.; Tona, A.; Elgendy, H.; Karim, A., and

Amis, E.J., “Combinatorial Characterization of

Biodegradable Polymers; Polymer Preprints, 2001;

42(1):273–274.

Migler, K. B., “Extrusion Visualization from Blend Structure

to Sharkskin”; Proc. of the Society of Plastics

Engineers 2001 Annual Technical Conference, 2001.

—, “String formation in sheared polymer blends:

Coalescence, breakup, and finite size effects”;

Physical Review Letters, 2001; 86:1023–1026.

Migler, K. B.; Lavallée, C.; Dillon, M. P.; Woods, S. S., and

Gettinger, C. L., “Visualizing the elimination of

sharkskin through fluoropolymer additives: Coating

and polymer-polymer slippage”; Journal of Rheology,

2001; 45:565–581.

—, “Flow Visualization of Polymer Processing Additive

Effects”; Proc. of the Society of Plastics Engineers

2001 Annual Technical Conference, 2001.

Morgan, A. B.; Jackson, C. L., and Gilman J. W.

“Characterization of the Dispersion of Clay in a

Polyetherimide Nanocomposite”; Macromolecules, in

press.

Nakatani, A. I.; Chen, W.; Schmidt, R. G., and Han, C. C.,

“Chain Dimensions in Polysilicate-Filled

Poly(Dimethyl Siloxane)”; Polymer, 2001; 42:3713–

3722.

Nakatani, A. I.; Ivkov, R.; Papanek, P.; Jackson, C. L.;

Yang, H.; Nikiel, L., and Gerspacher, M., “The

Significance of Percolation on the Dynamics of

Polymer Chains Bound to Carbon Black”; MRS

Symposium Proc., 2001.

Nakatani, A. I.; Ivkov, R.; Papanek, P.; Yang, H., and

Gerspacher, M., “Inelastic Neutron Scattering From

Filled Elastomers”; Rubber Chemistry and

Technology, 2000 Nov–2000 Dec 31; 73(5):847–863.

Nakatani, A. I.; Kwan, K. S.; Ivkov, R., and Papanek, P.,

“Silica Surface Treatment Effects on the Dynamics of

Poly(Dimethyl Siloxane) by Time-of-Flight Neutron

Spectroscopy”; Polymer Preprints, 2001; 42(1):176–

177.

Netz, P. A.; Starr, F. W.; Stanley, H. E., and Barbosa, M. C.,

“Static and Dynamic Properties of Stretched Water”;

Journal of Chemical Physics, 2001; 115(1):344–348.

Niranjan, P. S.; Forbes, J. B.; Greer, S. C.; Dudowicz, J., and

Douglas, J. F., “Thermodynamic Regulation of Actin

Polymerization”; Journal of Chemical Physics, 2001;

114:10573–10576.

Nyden, M. R.; VanderHart, D. L., and Alamo, R. G., “The

Conformational Structures of Defect-Containing

Chains in the Crystalline Regions of Isotactic

Polypropylene”; Computational and Theoretical

Polymer Science, 2001; 11:175–189.
 Publications 

59

Obrzut, J., “Dielectric Characterization of Embedded

Decoupling Capacitance Films at Microwave

Frequencies”; Proc. of the SMTA 6th Annual New &

Emerging Technologies for Electronic Packaging and

Assembly; Dallas, TX, 2000.

Obrzut, J., “ Embedded Capacitance Materials”; Embedded

Decoupling Capacitance Project Final Report, 2000

Dec.

Obrzut, J. and Nozaki, R., “Broadband Characterization of

Dielectric Films for Power-Ground Decoupling”; IEEE

Instrumentation and Measurements Technology,

Transactions Proceedings; Budapest, Hungary, 2001.

—, “Permittivity Measurements of Solid Film Dielectrics at

Microwave Frequencies”; IPC EXPO Technical

Conference; San Diego, CA, 2000.

Phelan, F. R., “Model Based Predictions of Permeability in

Preform Materials”; Proc. Society of Plastics

Engineers 2001 Annual Technical Conference, 2001.

Phelan, F. R.; Hobbie, E.; Jeon, H.; Glotzer, S. G., and Han,

C. C., “Modeling Drop Size Distribution in Polymer

Blend Injection Molding”; Proc. Society of Plastics

Engineers 2001 Annual Technical Conference, 2001.

Pochan, D. J.; Lin, E. K.; Satija, S. K., and Wu, W.-L.,

“Thermal Expansion of Supported Thin Polymer Films:

a Direct Comparison of Free Surface Vs Total

Confinement”; Macromolecules, 2001 Apr 24;

34(9):3041–3045.

Qiao, F.; Migler, K. B.; Hunston, D. L., and Han, C. C.,

“Reactive Compatibilization and In-line

Morphological Analysis of Blends of PET and a

Thermotropic Liquid Crystalline Polymer”; Polymer

Engineering and Science, 2001; 41:77–85.

Raghavan, D.; Gu, X.; Nguyen, T.; VanLandingham, M.,

and Karim, A., “Mapping Polymer Heterogeneity

Using Atomic Force Microscopy Phase Imaging and

Nanoscale Indentation”; Macromolecules, 2000; 33:

2573–2583.

Scala, A.; Starr, F. W.; La Nave, E.; Stanley, H. E., and

Sciortino, F., “Free Energy Surface of Supercooled

Water”; Physical Review E., 2000 Dec; 62(6):8016–

8020.

Schmidt, G.; Nakatani, A. I.; Butler, P.; Ferreiro, V.; Karim,

A., and Han, C. C., “Polymer-Clay Nanocomposite

Materials, Solution and Bulk Properties”; Proc. of the

Materials Research Society Symposium, 2001.

Schroder, T. B.; Sastry, S.; Dyre, J. C., and Glotzer, S. C.,

“Crossover to Potential Energy Landscape Dominated

Dynamics in a Model Glass-Forming Liquid”; Journal

of Chemical Physics, 2000 Jun 8; 112(22):9834–9840.

Schultheisz, C. R. and Leigh, S., “Certification of the

Rheological Behavior of SRM 2490, Polyisobutylene

Dissolved in 2,6, 10, 14 tetramethyl pentadecave;

NIST Special Publication 260–142, 2001.

Schultheisz, C. R. and McKenna, G. B., “Standard

Reference Materials: Non-Newtonian Fluids for

Rheological Measurements”; Proceedings of the

Society of Plastics Engineers 2001 Annual Technical

Conference; Volume 6, 1100–1104, Dallas, TX, May

2001.

Skrtic, D.; Antonucci, J. M.; Eanes, E. D., and Brunworth,

R. T., “Silica- and Zirconia-hybridized Amorphous

Calcium Phosphate. Effect on Transformation to

Hydroxyapatite”; Journal of Biomedical Materials

Research; in press.

Smith, A. P.; Carson, J. C.; Douglas, J. F., and Karim, A.,

“Combinatoric Study of Surface Pattern Formation in

Thin Block Copolymer Films”; Physical Review

Letters, 2001; 87:015503-1-4.

Smith, A. P.; Meredith, J. C.; Douglas, J. F.; Amis, E. J., and

Karim, A., “High-Throughput Characterization of

Pattern Formation in Symmetric Diblock Copolymer

Films”; Journal of Polymer Science: Polymer Physics;

in press.

Smith, A. P.; Sehgal, A.; Amis, E. J., and Karim, A.,

“Characterization of Surface Energy Effects on

Morphology of Thin Diblock Copolymer Films by

High Throughput Techniques”; Polymer Preprints,

2001.

Snyder, C. R., “High Sensitivity Technique for

Measurement of Thin Film Out-of-Plane Expansion.

II. Conducting and Semiconducting Samples”;

Characterization and Metrology for ULSI Technology:

2000 International Conference, 2000.

Soles, C. L.; Dimeo, R. M.; Neumann, D. A.; Kisliuk, A.;

Sokolov, A. P.; Liu, J. W., and Yee, A. F., “Correlations

of the Boson Peak With Positron Annihilation in

Series of Polycarbonate Copolymers”;

Macromolecules, 2001 Jun 5; 34(12):4082–4088.

Soles, C. L.; Douglas, J. F., Dimeo, R. M., and Wu W.-L.,

“The Dynamics of Confined Polycarbonate Chains

Probed with Incoherent Neutron Scattering”; Polymer

Materials Science and Engineering, 2001; 85.

Soles, C. L.; Lin, E. K.; Wu, W.-L.; Lin, Q., and

Angelopoulos, M., “Confinement Induced Deviation

in Ultra-thin Photoresist Films”; Proc. of the SPE

RETECH 12th Intl. Conf. on Photopolymers, 2001.
Publications

60

Starr, F. W. and Glotzer, S. C., “Simulation of Filled Polymer

Melts on Multiple Length Scales”; Proc. of Materials

Research Society, 2001; 661.

Starr, F. W.; Sastry, S.; La Nave, E.; Stanley, H. E., and

Sciortino, F., “Free Energy Surface of Supercooled

Water”; Physical Review E, 2001; 62:041201.

Starr, F. W; Schroeder, T. B., and Glotzer, S. C., “Molecular

Dynamics Simulation of a Polymer Melt with a

Nanoscopic Particle”; Macromolecules; in press.

Strawhecker, K. E.; Kumar, S. K.; Douglas, J. F., and

Karim, A., “The Critical Pole of Solvent Evaporation

on the Roughness of Spun Cast Polymer Films”;

Macromolecules, 2001; 34:4669–4672.

Tecklenburg, R. E.; Chen, H., and Wallace, W. E.,

“Electrospray FTMS and MALDI TOF MS

Characterization of a Methyl Silsesquioxane Resin”;

Proc. 49th ASMS Conference on Mass Spectrometry

and Allied Topics; in press.

Tesk, J. A., “NIST Reference Material for UHMWPE”,

Biomaterials Forum, 2001; 22(6):12.

—,“NIST Workshop on Reference Data for the Properties

of Biomaterials”; Journal of Biomedical Materials

Research, Applied Biomaterials, 2001; 58(4).

—,“Reference Data and Materials Needed”; Biomaterials

Forum, 2001; 22(6):11.

—,“Reference Materials for Tissue Engineered Medical

Products” in Tissue Engineering; in press.

VanderHart, D. L., “Solid State NMR Investigation of

Paramagnetic Nylon-6 Clay Nanocomposites I.

Crystallinity, Morphology and the Direct Influence of

Fe(+3) on Nuclear Spins; Chemistry of Materials; in

press.

—, “Solid State NMR Investigation of Paramagnetic

Nylon-6 Clay Nanocomposites II. Measurement of

Clay Dispersion, Crystal Stratification and Stability of

Organic Modifiers; Chemistry of Materials; in press.

VanderHart, D. L.; Asano, A., and Gilman, J. W., “NMR

Measurements Related to Clay-Dispersion Quality

and Organic-Modifier Stability in Nylon-6/Clay

Nanocomposites”; Macromolecules, 2001; 34:3819–

3822.

Wallace, W. E., “Polymeric Materials Interest Group

Workshop Report”; Proc. 49th ASMS Conference on

Mass Spectrometry and Allied Topics; in press.

Wallace, W. E.; Fischer, D. A.; Efimenko, K.; Wu, W.-L.,

and Genzer, J., “Polymer Chain Relaxation: Surface

Outpaces Bulk, Brookhaven National Laboratory

National Synchrotron Light Source 2000 Activity

Report, Technical Highlights”; Brookhaven National

Laboratory Technical Publication 52615, 2000.

—,“Polymer Chain Relaxation: Surface Outpaces Bulk”;

Macromolecules, 2001; 34:5081.

Wallace, W. E. and Guttman, C. M., “Data Analysis

Methods for Synthetic Polymer Mass Spectrometry:

Autocorrelation”; Journal of Research of the National

Institute of Standards and Technology; in press.

Wallace, W. E.; Guttman, C. M., and Antonucci, J. M.,

“Mass Spectroscopy of Spin-on-glass Low-k

Dielectric Precursors”; Polymer Preprints, 2001;

42(1):279–280.

Wallace, W. E.; Guttman, C. M.; Fanconi, B. M., and Bauer,

B. J., “MALDI MS of Saturated Hydrocarbon

Polymers: Polyethylene and Other Polyolefins”; Proc.

of the 49th ASMS Conference on Mass Spectrometry

and Allied Topics; Chicago, IL; in press.

Wang, G. Z. G.; Wang, H.; Shimizu, K.; Han, C. C., and

Hsiao, B. S., “Early Stage Crystallization in Poly

(Ethylene-co-Hexene) by SAXS/WAXD, DSC, OM

and AFM”; ACS, Polymer Materials Science and

Engineering, 2001, 85.

Wang, H.; Composto, R. J.; Hobbie, E. K., and Han, C. C.,

“Multiple Lateral Length Scales in Phase-Separating

Thin Film Polymer Blends”; Langmuir, 2001; 17:2857–

2860.

Wang, H.; Wang, G. Z. G.; Han, C. C., and Hsiao, B. S.,

“Simultaneous SAXS and WAXS Study of the

Isothermal Crystallization in Polyolefin Blends”; ACS,

Polymer Materials Science and Engineering, 2001, 85.

Washburn, N. R.; Simon, C. G.; Tona, A.; Elgendy, H. M.;

Karim, A., and Amis, E. J., “Co-extrusion of

Biocompatible Polymers for Scaffolds with Controlled

Morphology”; Journal of Biomedical Materials

Research; in press.

Weir, M. D.; Khatri, C. A., and Antonucci, J. M., “Facile

Synthesis of Hydroxylated Dimethacrylates for Use in

Biomedical Applications”; Polymer Preprints, 2001;

42(2).

Wetzel, S. J.; Guttman, C. M., and Girard, J. E., “The

Influence of Laser Energy of MALDI on the

Molecular Mass Distribution of Synthetic Polymers”;

Proc. of the 49th American Society for Mass

Spectrometry Conf.; Chicago, IL, 2001.
 Publications 

61

Wilson, P. T.; Briggman, K. A.; Stephenson, J. C.; Wallace,

W. E., and Richter, L. J., “Molecular Order at Polymer

Interfaces Measured by Broad-Bandwidth

Vibrationally-Resolved Sum-Frequency Generation

Spectroscopy”; Quantum Electronics and Laser

Science Conference 2001 Technical Digest; in press.

Wu, W.-L.; Lin, E. K.; Lin, Q. H., and Angelopolous, M.,

“Small-Angle Neutron Scattering Measurements of

Nanoscale Lithographic Features”; Journal of Applied

Physics, 2000 Dec 15; 88(12):7298–7303.

—,“Small-Angle Neutron Scattering Measurements of

Nanoscale Lithographic Features”; Polymer Preprints,

2001; 42(1):265–266.

Xu, H. H. K.; Quinn, J. B.; Smith, D. T.; Antonucci, J. M.;

Schumacher, G. E., and Eichmiller, F. C., “Dental Resin

Composites Containing Silica-Fused Whiskers:

Effects of Whisker-to-Silica Ratio on Fracture

Toughness and Indentation Properties”; Biomaterials;

in press.

Yang, S.; Mirau, P.; Pai, C. S.; Nalamasu, O.; Reichmanis,

E.; Lin, E. K.; Lee, H. J.; Gidley, D.; Frieze, W. E.; Dull,

T. L.; Sun, J., and Yee, A. F., “Design of Nanoporous

Ultra Low-Dielectric Constant Organosilicates by SelfAssembly”; ACS PMSE, 2001.

Yang, S.; Pai, C. S.; Nalamasu, O.; Reichmanis, E.; Mirau,

P.; Obeng, Y. S.; Seputro, J.; Lin, E. K., and Lee, H. J.,

“Design of a Nanoporous Ultra Low-Dielectric

Constant Organosilicate”; Proc. of the 7th Intl. Conf.

on Polymers in Electronic Packaging, 2001.

Zhang, Y.; Douglas, J. F.; Ermi, B. D., and Amis, E. J.,

“Influence of Counterion Valency on the Scattering

Properties of Highly Charged Polyelectrolyte

Solutions”; Journal of Chemical Physics, 2001;

114:3299-3313.
62

Polymers Division

Chief

Eric J. Amis

Phone: 301-975-6762

E-mail: eric.amis@nist.gov

Deputy Chief

Bruno M. Fanconi

Phone: 301-975-6769

E-mail: bruno.fanconi@nist.gov

NIST Fellow

Charles C. Han

Phone: 301-975-6772

E-mail: charles.han@nist.gov

Group Leaders

Electronics Materials

Wen-Li Wu

Phone: 301-975-6839

E-mail: wen-li.wu@nist.gov

Biomaterials

Francis W. Wang

Phone: 301-975-6726

E-mail: francis.wang@nist.gov

Multiphase Materials

Charles Han

Multivariant Measurement Method

Alamgir Karim

Phone: 301-975-6588

E-mail: alamgir.karim@nist.gov

Characterization and Measurement

Method Development

Wen-li Wu

Standards and Data

Bruno Fanconi

Internal Capabilities

Eric J. Amis, Acting

Processing Characterization

Kalman Migler

Phone: 301-975-4876

E-mail: kalman.migler@nist.gov
63

Research Staff

Amis, Eric J.

eric.amis@nist.gov

Neutron, x-ray and light scattering

Polyelectrolytes

Viscoelastic behavior of polymers

Dendrimers and dendritic polymers

Functional biomaterials

Antonucci, Joseph M.

joseph.antonucci@nist.gov

Synthetic and polymer chemistry

Dental composites, cements and adhesion

Initiator systems

Interfacial coupling agents

Remineralizing polymer systems

Ashley, Karen+

karenmashley@hotmail.com

Polymer thin films

Dewetting

Combinatorial measurements

Balizer, Edward+

Neutron, x-ray scattering

Polymer electrostriction

Barnes, John D.+

john.barnes@nist.gov

Gas and vapor transport in polymers

X-ray scattering

Computer applications in polymer measurements

Bauer, Barry J.

barry.bauer@nist.gov

Polymer synthesis thermal characterization

Neutron, x-ray and light scattering

Dendrimers, metallic ions nanocluster

Beers, Kathryn

kathryn.beers@nist.gov

Crystallization in thin films

Optical light scattering

Controlled/living polymerizations

Blair, William R.

william.blair@nist.gov

Polymer analysis by size exclusion

Chromatography

Mass spectrometry of polymers

Bowen, Rafael L.*

rafael.bowen@nist.gov

Adhesion

Dental composites

Novel monomer synthesis

Brunner, Lorenz

lorenz.brunner@nist.gov

Mass spectrometry of polymers

Chemical modification

Infrared spectroscopy

Bur, Anthony J.

anthony.bur@nist.gov

Dielectric properties of polymers

Fluorescence and optical monitoring of polymer

processing

Piezoelectric, pyroelectric polymers

Viscoelastic properties of polymers

Cantoni, Giovana+

giovanna.cantoni@nist.gov

Biomaterials and biopolymers

Polymer thin films

Tissue engineering

Carey, Clifton M.*

clifton.carey@nist.gov

Dental plaque

Microanalytical analysis techniques

Phosphate chemistry

Ion-selective electrodes

Chang, Shu Sing+

Thermal properties of polymeric and composite

materials

Composite process monitoring

Electronic packaging materials

Polymer phase transitions

Precision electrical and temperature measurements

Chen, Erqiang+

erqiang_chen@hotmail.com

Polymer morphology

Phase behavior of block copolymers

Polymer blends
Research Staff

64

Chen, Wei+

wchen2.email.com@dcrn.e-mail.com

X-ray and neutron scattering

Low dielectric constant material characterization

Cherng, Maria*

maria.cherng@nist.gov

Calcium phosphate biomaterials

Chiang, Chwan K.

c.chiang@nist.gov

Electroluminescent polymers

Residual stress

Impedance spectroscopy

Chiang, Martin Y.

martin.chiang@nist.gov

Computational mechanics (finite element analysis)

Strength of materials, fracture mechanics

Engineering mechanics of polymer-based materials

Bi-material interface

Chow, Laurence C.*

laurence.chow@nist.gov

Calcium phosphate compounds and biomaterials

Dental and biomedical cements

Solution chemistry

Topical dental fluorides

Crosby, Alfred

alfred.crosby@nist.gov

Polymer adhesion

Polymer fracture

Viscoelasticity

Elastomers

Block copolymers

Dähnhardt, Jan-Erik+

Self-curing dental repair resin

Davis, G. Thomas+

george.davis@nist.gov

Electronic packaging

Polymer crystallization

X-ray diffraction of polymers

Polarization distribution

Piezoelectricity in polymers

DeReggi, Aime S

aime.dereggi@nist.gov

Polarization-depth profiles in polymers

Space charge in dielectrics

Ferroelectric polymers

Polymeric piezo- & pyroelectric devices

Dickens, Sabine*

sabine.dickens@nist.gov

Dental composites

Dental adhesives

Transmission electron microscopy

Di Marzio, Edmund A.+

edmund.dimarzio@nist.gov

Statistical mechanics of polymers

Phase transitions

Glasses

Polymers at interfaces

Douglas, Jack F.

jack.douglas@nist.gov

Theory on polymer solutions, blends, and filled

polymers

Transport properties of polymer solutions and

suspensions

Polymers at interfaces

Scaling and renormalization group calculation

Dunkers, Joy P.

joy.dunkers@nist.gov

Optical coherence tomography

Image analysis

Fiber optic spectroscopy

Infrared microspectroscopy of polymers

Eanes, Edward D.+

edward.eanes@nist.gov

Structure of bones and teeth

Calcium phosphate compounds as dental materials

Effects of solution and biological molecules on

precipitation of calcium phosphates

Liposome studies

Eichmiller, Frederick C.*

frederick.eichmiller@nist.gov

Clinical dentistry

Composites

Dentin adhesives

Eidelman, Naomi N.*

naomi.eidelman@nist.gov

Prevention of calcification in the cardiovascular

system

Effect of phosphonates, cholesterol and

phospholipids on calcium phosphate formation

Characterization of calcified deposits by FTIR

microscopy

Esker, Alan R.+

alan.esker@nist.gov

Membrane mediated polymer interdiffusion

Phase separation kinetics of polymer blends
 Research Staff 

65

Fanconi, Bruno M.

bruno.fanconi@nist.gov

Infrared & Raman spectroscopy of polymers

Structure of polymers

Polymer fracture

Process monitoring of polymer composites

Feresenbet, Elias+

Silane deposition

Composite interfaces

Flaim, Glenn M.*

glenn.flaim@nist.gov

Fabricating dental composites

Floyd, Cynthia J. E.+

cynthia.floyd@nist.gov

Dental composites

Flynn, Kathleen M.

kathleen.flynn@nist.gov

Permeability measurements and database

Flow visualization experiments

Web page development

Fowler, Bruce O.+

bruce.fowler@nist.gov

Infrared and Raman spectroscopy

Structure of calcium phosphates, bones, and teeth

Composites

Frukhtbeyn, Stanislav+

Calcium phosphate compounds and biomaterials

Topical dental fluorides

Galvin, Agnes Ly.*

agnes.galvin@nist.gov

Clinical dental assistant

Adhesion measurements

George, Laurie A.*

laurie.george@nist.gov

Glass-ceramics

Giuseppetti, Anthony A.*

anthony.giuseppetti@nist.gov

Casting of dental alloys

Mercury-free amalgam alterative

Goldschmidt, Robert+

robert.goldschmidt@nist.gov

Mass spectrometry of polymers

Chemical analysis

Groehn, Franziska+

franziska.groehn@nist.gov

Neutron and x-ray scattering

Electron microscopy

Dendrimers

Nanocomposites

Nanocrystals

Organic-inorganic hybrids

Guttman, Charles M.

charles.guttman@nist.gov

Solution properties of polymers

Size exclusion chromatography

Mass spectroscopy of polymers

Han, Charles C.

charles.han@nist.gov

Phase behavior of polymer blends

Phase separation kinetics of polymer blends

Polymer characterization and diffusion

Shear mixing/demixing and morphology control

of polymer blends

Static, time resolved, and quasi-elastic scattering

of light and neutron

Hedden, Ronald

ronald.hedden@nist.gov

Siloxane polymers: synthesis and properties of

monomers, linear chains, and networks

Mechanical properties of elastomers

Polymer fractionation

Gel permeation chromatography

Hobbie, Erik K.

erik.hobbie@nist.gov

Light scattering and optical microscopy

Dynamics of complex fluids

Shear-induced structures in polymer blends and

solutions

Holmes, Gale A.

gale.homes@nist.gov

Composite interface science

Chemical structure-mechanical property

relationships for polymers

Polymer chemistry

Mass spectroscopy
Research Staff

66

Hunston, Donald L.

donald.hunston@nist.gov

Adhesion science and technology

Fracture behavior of polymers

Processing and failure behaviors of polymer

composites

Flow behavior of dilute high-polymer solutions

Macromolecular-small molecule binding

Hybrid-reinforced composites

Hussain, Latiff*

latiff.hussain@nist.gov

Monomer polymer synthesis, characterization,

testing

Dental composites, adhesives

Jeon, Hyun Sik+

hyunsik.jeon@nist.gov

Shear light scattering and optical microscopy

Structure and morphology of two-phase elastomer

blends under shear

Jianmei, He+

jianmei.he@nist.gov

Computational mechanics (finite element modeling)

Adhesive joints

Structural optimization

Jones, Ronald+

ronald.jones@nist.gov

Neutron and x-ray scattering

Neutron reflectivity

Polymer surfaces and thin films

Polymer phase transitions and computer simulation

Karim, Alamgir

alamgir.karim@nist.gov

Polymer fillers and nanocomposites

Patterning of thin-polymer blend films on

inhomogenous surfaces

Neutron and x-ray reflection, scattering,

AFM and optical microscopy

Thin-film phase behavior of polymer blends

Combinatorial thin-film polymer coatings

Kelly, J. Robert+

robert.kelly@nist.gov

Calcium phosphate cements

Dental ceramics

Failure analysis; dental prostheses

Finite element analysis

Weibull analysis

Kennedy, Scott B.+

scott.kennedy@nist.gov

Tissue engineering

Biomaterials

Block copolymers

Combinatorial surface patterns

Kennedy, Sharon L.

sharon.kennedy@nist.gov

Lithographically patterned surfaces

Biomaterials

Combinatorial patterned arrays

Combinatorial polymer blends

Combinatorial phase behavior of polymer blends

Khatri, Chetan A.+

chetan.khatri@nist.gov

Monomer/polymer synthesis and characterization

Khoury, Freddy A.

freddy.khoury@nist.gov

Crystallization, structure and morphology of

polymers

Analytical electron microscopy of polymers

Wide-angle and small-angle x-ray diffraction

Structure and mechanical property relationships

Kumar, Sanat+

kumar@plmsc.psu.edu

Polymer coatings and thin films

Simulations

Physical properties of polymers

Phase separation

Multiphase polymer systems

Lee, Hae-Jeong+

hae-jeong.lee@nist.gov

X-ray reflectivity

Small-angle neutron scattering

Synthesis and characterization of low dielectric

constant thin films

Lenhart, Joseph L.

joseph.lenhart@nist.gov

Sensors

Interphase structure

Li, Bizhong+

Polymer processing

Polymer blends

Polymer-clay processing

Liao, Nam S.*

nam.liao@nist.gov

Synthesis and testing of dental adhesives

Internal stress of composition due to polymerization
 Research Staff 

67

Lin, Eric K.

eric.lin@nist.gov

Statistical mechanics

X-ray and neutron reflectivity

Liu, D.-W.

da-wei.liu@nist.gov

Polymer synthesis

Thermal gravimetric analysis

Differential scanning calorimetry

Gel permeation chromatography

Infrared spectroscopy

Nuclear magnetic resonance

Scanning electron microscopy

Atomic force microscopy

Lynn, Gary W.+

gary.lynn@nist.gov

X-ray and neutron reflectivity

Optical microscopy

Mager, Carie+

carie.mager@nist.gov

Toughening bioceramics

Fracture mechanics

Markovic, Milenko*

milenko.markovic@nist.gov

Calcium phosphate chemistry

Biomineralization (normal and pathological)

Crystal growth and dissolution kinetics

Heterogeneous equilibria

Mathew, Mathai*

mathai.mathew@nist.gov

Crystallography

Calcium phosphate compounds

Maurey, John M.+

john.maurey@nist.gov

Ultracentrifugation

Rayleigh light scattering

Osmometry

Densimetry

Refractometry

Intrinsic viscosity

McDonough, Walter G.

walter.mcdonough@nist.gov

Processing and cure monitoring polymer composites

Failure and fracture of polymers

Polymer composite interfaces

McKenna, Gregory B.+

greg.mckenna@coe.ttu.edu

Failure, yield and fracture of polymers

Nonlinear viscoelasticity

Molecular rheology

Physics of polymer glasses

Rubber thermodynamics and mechanics

Mechanics of composites

Meredith, J. Carson+

james.meredith@nist.gov

Biodegradable polymer blends

Phase-separation and wetting properties of thin

films

Combinatorial methods for coatings

Migler, Kalman

kalman.migler@nist.gov

Effects of shear and pressure on phase behavior

Fluorescence and optical monitoring of polymer

processing

Liquid crystals

Shear-induced two phase structures

Polymer slippage

Mopsik, Frederick I.+

frederick.mopsik@nist.gov

Dielectric measurements and behavior

Automated measurement design

Computerized data analysis and programming

Electrical properties of polymers

Mueller, Herbert J. *

herb.mueller@nist.gov

Dental biomaterials

Interfacial interactions via electrochemical and

infrared spectroscopy

Chevron notch fracture toughness

Mechanical properties via nondestructive methods

Nakatani, Alan I.+

alan.nakatani@nist.gov

Polymer blends and solution properties under shear

Small-angle neutron scattering

Phase behavior of polymer blends

Filled polymers

Rheo-optical behavior of polymers

Noda, Natsuko+

natsuko.noda@nist.gov

Impendence spectroscopy

Dielectric characterization of composites
Research Staff

68

Nozaki, Ryusuke+

ryusuke.nozaki@charco.sci.hokudai.ac.jp

Dielectric relaxation in polymers

Impedence spectroscopy

Obrzut, Jan

jan.obrzut@nist.gov

Electronic properties of polymers and composites

Photoelectron spectroscopy (x-ray and UV)

Dielectric relaxation spectroscopy

Electronic packaging

Reliability, stress testing

Microwave and optical waveguides

Parry, Edward E.*

edward.parry@nist.gov

Dental appliance and crown and bridges fabrication

Machine shop applications

Pathak, Jai A.+

jai.pathak@nist.gov

Polymer rheology

Polymer dynamics

Glass transition

Polymer blends

Pfeiffer, Carmen+

carmen.pfeiffer@nist.gov

Dental resins

Monomer synthesis

Phelan, Jr., Frederick R.

frederick.phelan@nist.gov

Resin transfer molding: modeling and processing

studies

Viscoelastic flow modeling

Flow in porous media

Lattice Boltzmann methods

Pochan, Darrin+

pochan@udel.edu

SEM & TEM of polymeric materials

Wide-angle and small-angle x-ray scattering

Block copolymer phase behavior

Popielarz, Roman+

roman.popielarz@nist.gov

Polymer synthesis and characterization

Photo-polymerization

Qiao, Fang+

Polymer mixing and compounding

Liquid crystalline polymer/thermal plastic polymer

 mixing

Roth, Steven C.

steven.roth@nist.gov

Piezoelectric polymer transducers-fabrication and

applications

Vacuum deposition of metals

Calibration of polymer transducers

Microcomputer interfacing

Fluorescence measurements

Schmidt, Gudrun+

gudrun.schmidt@nist.gov

Polymer blends

Liquid crystalline polymers

Polymer-clay interaction

Light and neutron scattering

Schultheisz, Carl R.

carl.schultheisz@nist.gov

Failure of composites

Experimental mechanics

Torsional dilatometry

Physics of polymer glasses

Polymer rheology

Schumacher, Gary E.*

gary.schumacher@nist.gov

Clinical dentistry

Composites

Dentin adhesives

Sehgal, Amit+

amit@nist.gov

Biomaterials, cell-surface biophysics

Polymer thin films

Polyelectrolytes and conducting polymers

Structure and dynamics of polymer solutions

Light scattering and fluorescence photobleaching

recovery

Shi, An-Chang +

shi@polymer.physics.mcmaster.ca

Colloid theory

Polymer phase transitions

Sieck, Barbara A.*

barbara.sieck@nist.gov

Calcium phosphate compounds

Chemical analysis

Remineralization

Simon, Carl G., Jr.

carl.simon@nist.gov

Biocompatibility

Cytotoxicity

Signaling in human platelets

Bone marrow cell lineage/trafficking
 Research Staff 

69

Skrtic, Drago*

drago.skrtic@nist.gov

Calcium phosphates as dental materials

Liposome studies

Smith, Archie+

archie.smith@nist.gov

Combinatorial (high-throughput) experimental

design and development

Polymer crystallization behavior

Thin-film block copolymer behavior

Nanofilled polymer behavior

Electron, atomic force, x-ray and light microscopies

Snyder, Chad R.

chad.snyder@nist.gov

Polymer crystallization

WAXD and SAXS of polymeric materials

Thermal expansion measurements

Thermal analysis of polymers

Dielectric measurements and behavior

Soles, Christopher

csoles@nist.gov

Viscoelastic properties of polymers

Elastic and inelastic neutron scattering

X-ray and neutron reflectivities

Polymer thin films

Son, Younggon +

Younggon.son@nist.gov

Polymer processing

Polymer phase behavior

Interfacial phenomena

Stafford, Christopher+

chris.stafford@nist.gov

Polymer adhesion

Surfaces and interfaces

Polymer thin films

Stansbury, Jeffrey W.

jeffrey.stansbury@nist.gov

Synthetic chemistry

Polymers and polymer composites

Polymerization of expanding monomers

Fluorinated polymers

Polymerization kinetics

Starr, Francis

francis.starr@nist.gov

Dynamics of filled polymers

Slow dynamics in soft condensed matter

Molecular dynamics simulations and parallel

computing

Takagi, Shozo*

shozo.takagi@nist.gov

Crystallography

X-ray diffraction

Calcium phosphate biomaterials

Topical fluoridation

De- and remineralization

Tesk, John A.

john.tesk@nist.gov

Biomaterials: industrial relations

Bond strength characterization

Casting of alloys

Strength of dental systems

Thermal expansion and properties of dental materials

Finite element studies

Porcelain-metal systems

Weibull analysis

Wear testing, orthopaedic materials

Reference biomaterials

Tung, Ming S.*

ming.tung@nist.gov

Chemistry of calcium phosphate compounds

Remineralization studies

Standard reference materials

VanderHart, David L.

david.vanderhart@nist.gov

Measurement of orientation in polymer fibers and

 films

Solid-state NMR of polymers

Measurement of polymer morphology at the

2–50 nm scale

Pulsed field gradient NMR

Van Zanten, John H.+

jhvanzan@unity.ncsu.edu

Complex fluids

Polymer interfaces

Scattering of light, neutrons & x rays

Biophysics

Interfacial phenomena

Scanning-probe microscopy

Vogel, Gerald L.*

gerald.vogel@nist.gov

Dental plaque chemistry, chemistry of calcium

phosphates

Microanalytical techniques
Research Staff

70

Wallace, William E.

william.wallace@nist.gov

Surface and interface behavior

Ion beam and electron spectroscopies

X-ray and neutron reflectivity

MALDI mass spectrometry

Wang, Francis W.

francis.wang@nist.gov

Photophysics and photochemistry of polymers

Fluorescence spectroscopy

Cure monitoring of polymerization

Tissue engineering

Wang, Howard +

hao.wang@nist.gov

Multiple phase transitions in polymer

Wetting, segregation and transport in polymer

Structure and dynamics in polymer gels

Washburn, Newell

newell.washburn@nist.gov

Tissue engineering

Polymer blends

Biomaterial interfaces

Viscoelastic properties of polymers

Weaver, Alia+

alia.weaver@nist.gov

Mass spectrometry of polymers

Weir, Michael

michael.weir@nist.gov

Biomaterials

Tissue engineering

Biodegradable hydrogels

Combinatorial analysis

UV and fluorescence spectroscopy of polymers

Wetzel, Stephanie

stephanie.wetzel@nist.gov

Mass spectrometry of polymers

Data analysis

Chemometrics

Wu, Wen-li

wen-li.wu@nist.gov

Neutron and x-ray scattering and reflectivity

Electron microscopy

Mechanical behavior of polymers and composites

Polymer surfaces and interfaces

Yurekli, Koray+

kyurekli@Jetson.uh.edu

Polymer nanocomposite

Phase separation

Thin films and interfaces

Neutron and light scattering

Xie, Baosheng+

Testing micro tensile and micro-sheer bond strength

Xu, Huakun*

hockin.xu@nist.gov

Silver alloy alternative to amalgam

Wear and fatigue

Fiber and whisker reinforcement

Zhang, Yubao+

yubao.zhang@nist.gov

Dynamic light scattering

Polyelectrolytes

Small-angle neutron scattering

*Research Associate

+

Guest Scientist
71

Organizational Charts

Materials Science and Engineering Laboratory

L.E. Smith, Director

D.E. Hall, Deputy Director

Ceramics

S.W. Freiman, Chief

S.J. Dapkunas, Deputy

Materials Reliability

F.R. Fickett, Chief

T.A. Siewert, Deputy

NIST Center for

Neutron Research

J.M. Rowe, Director

National Institute of Standards and Technology

Director

Boulder Laboratories

Director for

Administration

& Chief Financial Officer

Technology

Services

Advanced

Technology

Program

Manufacturing

Extension

Partnership

Manufacturing

Engineering

Laboratory

Chemical

Science and

Technology

Laboratory

Materials

Science and

Engineering

Laboratory

Electronics and

Electrical

Engineering

Laboratory

Information

Technology

Laboratory

Physics

Laboratory

Building and

Fire Research

Laboratory

Polymers

E.J. Amis, Chief

B.M. Fanconi, Deputy

Baldrige National

Quality Award

Director

Deputy Director

Metallurgy

C.A. Handwerker, Chief

F.W. Gayle, Deputy
72

Organizational Charts

Polymers Division (854.00)

Eric Amis, Division Chief

Bruno Fanconi, Deputy Chief

Donna Stutso, Administrative Officer

Dawn Bradley, Division Secretary

Sheila St.Clair, Office Automation Assistant

Characterization & Measurement (854.01)

Bronny Webb, Secretary

Method Development

Wen-li Wu

M. Byrd

M. Chiang

J. Dunkers

R. Hedden

R. Jones

F. Landis

J. Lenhart

S. Lin-Gibson

F. Starr

W. Wallace

Standards & Data

Bruno Fanconi

W. Blair

C. Guttman

C. Schultheisz

J. Tesk

L. Brunner

R. Goldschmidt

J. Maurey

A. Weaver

A. Wetzel

Internal Capabilities

Eric Amis, Acting

B. Bauer

A. DeReggi

J. Douglas

S. Hudson

F. Khoury

D. Liu

W. McDonough

P. McGuiggan

D. Vanderhart

Electronics Materials (854.02)

Wen-li Wu, Group Leader

Bronny Webb, Secretary

Biomaterials (854.03)

Francis Wang, Group Leader

June Burton, Secretary

Multiphase Materials (854.04)

Charles Han, NIST Fellow

June Burton, Secretary

Processing Characterization

(854.05)

Kalman Migler, Group Leader

Karen Hollingsworth, Secretary

Multivariant Measurement

Methods (854.06)

Alamgir Karim, Group Leader

Karen Hollingsworth, Secretary

H. Lee

N. Noda

R. Popielarz

W. Sakai

C. Chiang

E. Lin

J. Obrzut

C. Snyder

C. Soles

J. Antonucci

J. Hsii

C. Simon

M. Weir

M. Farahani

B. Fowler

C. Khatri

A. Mizukami

N. Yamamoto

S. Yoneda

A. Bur

K. Flynn

S. Roth

J. Pathak

Y. Son

E. Hobbie

G. Holmes

D. Hunston

F. Phelan

E. Feresenbet

J. He

H. Kim

C. Moon

G. Schmidt

K. Shimizu

H. Wang

Z. Wang

K. Beers

A. Crosby

S.L. Kennedy

N. Washburn

K. Ashley

G. Cantoni

S.B. Kennedy

A. Sehgal

A. Smith

K. Yurekli
NISTIR 6796—POLYMERS DIVISION: FY 2001 PROGRAMS AND ACCOMPLISHMENTS