On the Cover:

From the front cover and continuing on to the back, the images shown are,

respectively: (1) a finite element simulation of interfacial debonding of a

combinatorial test library; (2) a synchrotron x-ray scattering pattern of a

nanostructured thin film for electronic applications; (3) a lattice Boltzmann

simulation of the breakup of a stationary string under simple shear flow in a

polymer emulsion between parallel plates; (4) polarized light scattering

patterns from multiwalled carbon nanotubes dispersed in a polymer matrix

under shear; (5) atomic force (top) and fluorescence microscopy (bottom)

images of poly(l-lactic acid) annealed over a temperature range and the cell

growth on it after uniform seeding; and (6) a series of Gel Permeation

Chromatography (GPC) curves on six polyethylene Standard Reference

Material (SRM) fractions. More information about each of these topics can

be found within this report.
i

Materials Science and

Engineering Laboratory

FY 2002 Programs and

Accomplishments

Polymers

Division

Eric J. Amis, Chief

Bruno M. Fanconi, Deputy

Chad R. Snyder, Deputy

NISTIR 6906

September 2002

National Institute of

Standards and Technology

Arden L. Bement, Jr.

Director

Technology

Administration

Phillip J. Bond

Undersecretary of

Commerce for Technology

U.S. Department

of Commerce

Donald L. Evans

Secretary
Certain commercial entities, equipment, or materials may be identified in this document

in order to describe an experimental procedure or concept adequately. Such identification

is not intended to imply recommendation or endorsement by the National Institute of

Standards and Technology, nor is it intended to imply that the entities, materials, or

equipment are necessarily the best available for the purpose.
iii

Table of Contents

Table of Contents

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

Technical Highlights:

Polyolefins: Serving the Largest Market ..................................................................... 3

Micro-Confined Blends .............................................................................................. 6

Pore Size Distributions in Low-k Dielectric Thin Films

from X-ray Porosimetry .............................................................................................. 8

Direct Measurement of the Reaction Front in

Chemically Amplified Photoresists ............................................................................ 10

Metrologies for Tissue Engineering ........................................................................... 12

NIST Combinatorial Methods Center ........................................................................ 14

Advanced Manufacturing Methods .................................................................................. 17

Control of Extrusion Instabilities ................................................................................ 18

Process Monitoring of Polymer/Clay Nanocomposites ................................................ 19

Liquid Crystalline Nanostructures:

Phase Behavior and Processing ................................................................................ 20

Combinatorial Methods .................................................................................................. 21

Combinatorial Adhesion and Failure .......................................................................... 22

High-Throughput Mechanical Properties of Polymer Films .......................................... 23

Mapping the Effects of a Nucleating Agent on

Polymer Crystallization ............................................................................................. 24

Interface of Materials with Biology .................................................................................. 25

Structure–Property Relationships in Dental Polymers ................................................. 26

Characterization and Modeling of Tissue Engineering Scaffolds .................................. 27

Metrology for Tissue Engineering .............................................................................. 28

Materials for Micro- and Optoelectronics ........................................................................ 29

Characterization of Porous Low-k Dielectric Constant Thin Films ............................... 30

Dielectric Metrology for Polymer Composite Films

in the Microwave Range ........................................................................................... 31

Polymer Photoresists for Next-Generation Lithography .............................................. 32
iv

Table of Contents

Materials Property Measurements .................................................................................. 33

Characterization and Modeling of Failure in Fiber Composites ................................... 34

Materials Structure Characterization ............................................................................... 35

Polymer Standards .................................................................................................. 36

Polyolefin Mass Spectrometry................................................................................... 37

Multi-Modal Imaging Using Optical Coherence Tomography ....................................... 38

Quantifying Dispersion and Properties of

Carbon Nanotube Composites .................................................................................. 39

Characterization and Modeling of the Interfaces and

Interphases of Polyolefin Blends ............................................................................... 40

Polymers Division FY02 Annual Report Publication List ................................................... 41

Polymers Division .......................................................................................................... 53

Research Staff .............................................................................................................. 54

Organizational Charts .................................................................................................... 63
1

Executive Summary

Executive Summary

The projects in our Division are

selected by evaluating current and

future needs of industries through

workshops, industry roadmaps,

visits to companies and other

research organizations, and a

variety of other means. In addition,

much of our research is performed

in collaboration with customers. To further enhance

these types of collaboration and to increase the success

of technology transfer, a NIST-wide effort centered

in the Polymers Division, the NIST Combinatorial

Methods Center (NCMC), was formally established

in January 2002. The Center provides a portal for

demonstrating our cutting edge combinatorial materials

research effort. Examples of recent NCMC research

efforts include new methods for rapidly quantifying

over a range of conditions, the mechanical properties

of thin films, adhesion and failure mechanisms, and

crystallization kinetics.

As part of our ongoing

assessment of current and

future needs, the Polymers

Division, and NIST as a whole,

have identified nanotechnology

and health care as two critical

areas for investment. While

nanotechnology is not an

industry per se, the technology it represents is at the

heart of many growing industries. Key to enabling

the practical applications of nanotechnology will be

the ability to reliably manufacture nanoscale structures.

Due to the ever-pressing drive of Moore’s Law,

the semiconductor electronics industry is at the

forefront of this technology. As size scales shrink,

the associated tolerances also shrink. Electronics are

rapidly approaching the point at which sub-100 nm

structures are needed. Control of the photolithographic

process at this size-scale is painfully exquisite with

dimensional tolerances on the order of the size of

the polymer molecules. Headed by a recent winner of

the Presidential Early Career Award for Scientists

and Engineers (PECASE) and in collaboration with

key industrial partners, our Electronics Materials

Group is developing experimental methods needed to

characterize chemical transport and materials science

phenomena over nanometer length scales. Another

project supporting the semiconductor electronics

industry has developed a solvent porosimetry technique

using x-ray reflectivity to calculate the pore-size

distribution in “low-k” nanoporous materials being

developed for the next generation of integrated circuits.

The advent of controlled

polymerization, advanced

electronics, biomimetic

materials, nanostructured

systems, and a range of other

new avenues for polymeric

materials has raised the

bar for measurements and

standards research. This report of the 2002 activities

and accomplishments describes many of the projects

designed by the scientists in the Polymers Division

at NIST to creatively meet this ongoing challenge.

As usual, our research encompasses a range of topics

and only a selection can be presented in this summary,

and we are also able to discuss only a fraction of

the many interactions with complementary teams

throughout NIST, with our industrial partners, and

with the larger scientific community. I encourage you

to consult our website at www.nist.gov/polymers for

more information.

As the “everyman”

polymers, polyolefins have

seen a resurgence of interest

and importance with the

development of new catalysts

with more precise molecular

control. The Polymers

Division is pioneering

measurements of absolute molecular mass distribution

of these polymers through the laser vaporization and

ionization methods of mass spectrometry. A mainstay

of analysis for organic molecules and biological

macromolecules, mass spectrometry is particularly

challenging for some common polymers such as

polyethylene because of their simple molecular

structure. Nevertheless, this year we have produced

intact gas phase polyethylene single chains with over

six times greater mass than previously reported by

any researchers. This is one example of how the

Polymers Division provides critical measurement

methods, standards, and fundamental concepts to

enable polymer-based technologies.
2

Another class of

nanostructured materials

is the broad range of

nanocomposites that have

potential uses ranging

from materials for wireless

communication, to gas

barrier materials, to

structural composites. Despite their intriguing potential,

there remain several fundamental problems in reaching

practical success. One such problem is the dispersion

and alignment within the polymer matrix of nanoparticles

and nanotubes. In Division projects, work has begun to

relate online optical measurements of carbon nanotube

composites and dielectric measurements of nanoclay

composites with a full suite of characterizations by

transmission electron microscopy, x-ray scattering,

and small-angle neutron scattering measurements.

The goal is to provide predictive measurement tools

to relate processing parameters to the microstructure

of nanocomposite materials. Our recent success in

developing broadband dielectric metrology extending

into the GHz region complements this work by allowing

similar quantification in composites formed with

ferroelectric ceramics.

For over 70 years,

NIST has had a successful

collaboration with the

American Dental Association

(ADA). Today, our efforts

in dental materials are

focused on determining

how monomer structure,

composition, and initiator affect the ultimate dental

composite properties. At the same time, we are

vigorously extending this work, more broadly, to address

critical issues at the interface of materials science with

biology. We are using our expertise in combinatorial

methods for rapid quantification of cell interactions

with synthetic biomaterials. Complementing this work,

we are developing in vitro tests for cell infiltration,

mechanical properties, and inflammatory response of

polymer scaffolds for tissue engineering. Successful

tests of this sort would lower R&D costs by reducing

the need for in vivo animal model tests. To characterize

the response of cell attachment and proliferation, we are

developing visualization by multimodal microscopies and

optical tomography. Currently, we have demonstrated a

combination of three hybrid techniques based on optical

coherence tomography for imaging of fluorescent markers

as well as structure within tissue scaffold materials.

In 2002, the Polymers Division has continued

to extend its work into new areas and strengthen

projects within our core programs. From health care

to manufacturing, we see many challenges for polymer

technology. The creativity of our researchers is assuring

that our research remains at the cutting edge of polymer

science, and our pervasive commitment to NIST’s

mission guides our choices from among the many

exciting opportunities for advances in soft materials

research.

As always, I welcome your comments on our

programs.

Eric J. Amis

Chief, Polymers Division

Executive Summary
3

Technical Highlights

Polyolefins: Serving the Largest Market

Polyolefins, primarily polyethylene and polypropylene,

comprise the largest share of the U.S. market for

polymers. Demand for the newer metallocene

polyolefins is expected to grow 20 percent per year

through 2006. The Polymers Division develops a

variety of measurement tools and concepts to meet

the broad needs of this diverse industry. Below,

the program is broken down into four interrelated

components: molecular characterization, microscopic

structure, processing, and physical properties. Each

component addresses the needs of different industrial

segments, but together they provide a backbone for

continued growth. While each component has focused

on polyolefins, there is a broader applicability of

the research.

Materials Science and Engineering Laboratory research

and services in molecular characterization provide

industry with the tools to properly ascertain molecular

mass and distribution. Calibration of instruments with

National Institute of Standards and Technology standard

materials allows suppliers and processors to trade with

confidence. Research into next generation calibration

techniques ensures that U.S. industry will maintain its

competitiveness as increasingly stringent demands are

placed upon materials producers.

SRMs for Molecular Characterization

Figure 1: Six narrow polyethylene fractions, with the

molecular mass moments obtained by absolute methods,

are used for calibration of instrumentation and for research.

Plotted is the differential refractive index (DRI) versus

elution volume in mL.

Molecular Characterization

The increasing number of distinct polyolefin

 molecules that have entered the marketplace, and

the larger number that can now be synthesized in the

laboratory, drive the need for characterization techniques;

in particular with respect to molecular mass and distribution.

These quantities determine the processability as well as

the final properties of the material.
4

Mass Spectrometry of Polyethylene

Polyethylene is not amenable to analysis by the

usual mass spectrometric methods owing to the lack

of chemical functionality to yield intact macromolecular ions.

In the last year, the polyolefin mass spectrometry

team produced intact, gas-phase polyethylene single

chains more than six times greater in mass than

previously reported by any research group.

Matrix-assisted laser desorption /ionization

time-of-flight mass spectrometry (MALDI-TOFMS) and the covalent cationization method,

developed last year in the Polymers Division,

were each optimized by a multidisciplinary team

of Division scientists. A palette of spectroscopic

techniques was used to find the optimal conditions

for the necessary conversion of polyethylene into its

ionizable phosphonium salt.

Microscopic Structure

Figure 2: Mass spectrum of SRM 1482 obtained by the

covalent cationization method. The insert shows details

of the spectrum above 15,000 g/mol showing that the

technique sees higher molecular mass species but not in the

correct proportion. Plotted is signal intensity in arbitrary

units (au) versus mass in u.

The molecular mass moments determined

from mass spectrometry are about two-thirds as

large as those found classically. This discrepancy

may be due, in part, to the highly crystalline nature

of the polyethylenes examined that may reject the

MALDI matrix during target preparation. In order

to prevent this occurrence, a heated sample stage

will be fitted to a TOF mass spectrometer allowing

experiments to be performed above the melting

temperature of polyethylene. In addition, experiments

on the covalent cationization of atactic polystyrene

are being undertaken in order to rule out effects

solely derived from the ionization process. This

project enjoys keen interest from industrial producers

who have offered to synthesize specialized materials

to further the Division’s work.

Figure 3: Structural information regarding polymer blends

under shear flow is obtained via in situ light scattering,

where HH indicates horizontal incident and scattered light

polarization, and VV is vertical light polarization.

Influence of Monomer Structure on Polymer Blend

Many commercially important polymer materials are

“alloys” of polymers having different monomer structures.

Flory-Huggins theory has provided the main theoretical

framework for describing the miscibility, phase separation

and scattering properties of polymer blends, but this theory

completely neglects the dissimilarity of monomer structure.

This fundamental issue was taken up in collaboration

with the University of Chicago. A generalization of the

Flory-Huggins theory, accounting for monomer structure

for high molecular weight (incompressible) blends, indicates

that monomer structure has profound effects on blend

properties and miscibility. We discovered a new classification

scheme, featuring four distinct classes of blends.

A re-analysis of earlier experimental studies from

the Polymers Division provides strong evidence for

this new theoretical framework.

Complex microscopic structures due to crystallization,

phase separation, and particulate dispersion directly

determine physical properties such as permeability, impact

strength, and toughness. The various microstructures are

developed during processing operations and reflect the

molecular characteristics of the polyolefin such as monomer

regularity and chain branching.

During the past year, extensive experimental work has

been carried out to understand the effect of blending and

thermal history on structure development in polyolefin

blends. This represents the first comprehensive

investigation of blends that exhibits both liquid phase

separation and crystallization. Among many interesting

findings, we mention just two. First, an abnormally large

effect of co-crystallization in this blend, which is not

expected if truly random copolymerization, is assumed.

Second, the effect of simple shear flow on crystal

suspensions in polyolefin blends has been investigated

using light scattering (see figure below) and microscopy.

The rich complexity of structure that we observed

demonstrates the potential for directed control of

microstructure through thermal and shear history.

Technical Highlights
5

Macroscopic Processing Physical Properties

SRMs for Processing

Virtually all polyolefins are specified by their melt flow

index (MFI). NIST produces melt flow rate standards that

are used for checking an ASTM method (ASTM D1238)

commonly used to determine processability of polyethylenes.

Figure 4: Instrumentation takes simultaneous

measurements of polyethylene rheology and temperature.

One primary reason for the size of the polyolefin

market is that numerous processing techniques have been

developed which provide the bridge between the raw

polymer and the final product. Processing considerations

force strong constraints upon new polymer development,

for example, frequently a new polymer molecule or

formulation must be processable with existing equipment

in order to succeed in the market. We frequently work

closely with the polyolefin industry on well-focused topics

o ensure the commercial relevance of our work.

One frequent concern in the processing of polyethylene

is its susceptibility to “sharkskin melt fracture” during

extrusion. We have utilized and developed instrumentation

to conduct precise measurements of the cause and location

of this processing defect. Current work includes the

construction of a Total Internal Reflection Coating

Instrument, which will be able to quantitate the buildup

of fluoropolymer additives, which is one strategy to

eliminate sharkskin.

A second critical issue in polyolefin processing is

the shear induced temperature excursions which can

significantly alter the viscosity and hence the processing.

Previously, we have developed fluorescent-based techniques

to conduct in situ measurements of polymer temperature

during extrusion. Recently, we have utilized this

methodology to carry out simultaneous measurements

of polyethylene rheology and temperature (see Figure 4).

We find that during a standard ASTM test method, the

resin temperature can increase uncontrollably by 20oC,

meaning that great care must be taken in the application

of the generated data.

A third area concerns molecular orientation during

polypropylene film production. Using fluorescent probes

that can orient with the extensional flow, we make fiber

optic-based sensors which determine the anisotropy of

the material.

Physical properties are a result of molecular

structure, microstructure and processing history.

Here we describe two activities intended to improve

the final properties.

Flammability of Polypropylene-Nanotube Composites

There is much current interest in the enhancement

of physical properties of polymeric materials by

incorporation of nano-scale additives, such as carbon

nanotubes and clay. In conjunction with the Fire

Research Division, we have recently shown that carbon

nanotubes can significantly reduce the heat release rate

of polypropylene under controlled burning conditions.

This work was carried out with multi-walled nanotubes

that were well dispersed at a 1% volume fraction,

without the addition of compatiblizers or organic

treatments of the nanotubes. Preliminary measurements

indicate that the fire suppression effectiveness is better

than achieved for clay filler nanocomposites at much

higher loadings (order 10% to 20% volume fraction),

where surfactant is required for effective clay dispersal.

The rapidly decreasing cost of the multi-walled carbon

nanotubes and the advantages of these composites

for recycling make this approach to fire suppression

potentially attractive for commercial development in

the future. Fire suppression in polyolefin materials,

in particular, is a problem of crucial importance to

society because of the widespread use of these

materials and the pollution associated with existing

fire retardant agents.

SRMs for Orthopedic Implants

Concerns about long-term durability of polyethylene

hip implants have created a need for a standard material

to test the properties of implant materials. In response,

the first reference biomaterial, an orthopedic grade

ultrahigh 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. Properties reported are the

Tensile Young’s Modulus, Yield Strength, Ultimate

Strength, and Elongation to Failure. In anticipation

of continuing need for reference material UHMWPE

for radiation studies, NIST issues orthopedic grade

UHMWPE cubes for radiation cross-linking tests

and analysis.

For More Information on this Topic

Molecular Characterization: B. Fanconi, C. Guttman,

W. Wallace; Microscopic Structure: J. Douglas, C. Han,

H. Wang; Macroscopic Processing: A. Bur, K. Migler;

Physical Properties: J. Douglas, J. Tesk

Technical Highlights
6

Micro-Confined Blends

Microscale processing is an emerging technology

with unique challenges and applications in polymer

processing and microfluidics industries, but the

physics of processing emulsions when the drop

size is comparable to a sample dimension is poorly

understood. We are developing predictive models

as we measure the effect of confinement and

flow on the distribution and morphology of one

component in another.

Fluid strings, which can be observed during typical

 polymer processing operations, develop prominence

in confined systems (Figure 1). The formation and

stability of strings is being understood through unique

observations of micro-confined polymer blends.

droplets produced. Direct observation of this phenomenon

in simple shear flow has not been reported thus far.

Figure 1: Strings in a flowing emulsion: a larger

confinement stabilized string is shown at left, and a smaller

string that is stabilized by shear alone is shown at right.

The scale bars represent the gap spacing between the flow

cell boundaries, 36 μm and 100 μm, respectively. After

stopping shear, the string at right breaks on timescales

on the order of 10 s, whereas breakup of the confinement

stabilized string requires timescales on the order of 1000 s.

Their stability arises from the effects of shear and

confinement. We are exploring the stability of bulk,

unconfined strings, as we directly test a recent theory

that predicts a new regime of processing conditions

wherein strings are stable. Confinement greatly

promotes the stability of strings, because the relaxation

and breakup rate is suppressed several fold due to

hydrodynamic interactions between the string and the

wall (Figure 2).

In addition, we are also making direct observations

of the mechanism of breakup of bulk strings (classical

Rayleigh–Tomotika instability and end pinching) in

simple shear flow. Direct comparisons will be made

between our experimental data and predictions of

hydrodynamic theories on quantities such as the time

taken to break up by a string and the size of the final

Figure 2: Lattice Boltzmann simulation of the breakup

of a stationary string confined between parallel plates.

Simulation results agree in detail with experimental

observations of the string shape and breakup rate.

Notice the ellipsoidal cross section of the string.

Figure 3: Morphology diagram describing microstructure in

confined PDMS /PIB (polydimethylsiloxane /polyisobutylene)

emulsions in the parameter space of mass fraction and shear

rate, for a uniform gap-width (36 μm) and a fixed viscosity

ratio (λ = 1). Points denote shear rates where experimental

data were obtained, and smooth curves are guides to the

eye drawn by the authors to demarcate regions of different

microstructure. Shaded points denote experimental

observation of ordered pearl-necklace chains of droplets.

In confined blends, the formation of strings is

facilitated by migration of drops away from the walls,

which leads to enhanced concentration and coalescence

Technical Highlights
7

of drops in the center of the flow channel. When

coalescence is inhibited either by increasing the flow

rate or by decreasing the total concentration of drops,

interesting new arrangements of drops are discovered

(Figure 3). At low drop concentration, pearl necklace

structures form (Figure 4). At higher shear rates, the

drops arrange into two layers that slide by one another.

Although the drop migration effect pushes drops toward

the center plane between the confining boundaries,

collisions between drops push them apart so that

separate layers are maintained.

As the drops become smaller at still higher rates

due to breakup, collisions become more numerous

and random, inducing random diffusive motion of the

droplets transverse to the flow. The spatial distribution

of drops under such conditions results from the

interplay of this diffusive motion and migration away

from the walls (Figure 5). By integrating the non-linear

convective-diffusion drop-transport equation, an

analytical expression is obtained for the steady state

droplet concentration. The degree to which the

drops are concentrated to the center depends on

the dimensionless parameter Pe. At steady state,

we derive the following volume fraction profile:

Pe = Ca (a/h) (4α /(fgy fφo) , where Ca is the capillary

number, a is the average drop radius, h is the spacing

between plates, α is a function of viscosity ratio, fgy

is the dimensionless diffusivity, y is a dimensionless

position, and φo is the nominal volume fraction of

dispersed phase (Figure 5).

Figure 5: Dispersed phase concentration as a function of

dimensionless position across the gap in which the emulsion

flows, shown here for Pe = 2.4. Results of theory (curve)

and experiment (symbols) are in good agreement. Near the

walls, the emulsion is denuded of drops, having important

implications for materials properties, including the surface

finish of extruded polymer materials. A recently published

linearized theory (gray curve) is not nearly as accurate.

( ) 















− φ = φ + − − 2

2

c

1 4y'

1

2

y' ' y' ' Pe 1

As implied above, interfacial properties and

coalescence phenomena have a large influence over

the morphology that develops in microscale processing.

Coalescence rates are measured through observation

of the evolution of the drop size distribution following

a step down in shear rate. Governing dimensionless

parameters and the effect of associated material

parameters are determined. In experiments involving

weakly adsorbed surfactant, we find that, at small

capillary number, the coalescence rate is limited by

diffusion-limited sorption, and at high capillary

number, when collision causes slight drop deformation,

coalescence is arrested by drop interface immobilization.

These measurements and observations

demonstrate that a remarkable variety of phenomena

occur in micro-confined blends. We plan to develop new

tools, based in part on these phenomena, to investigate

interfacial properties. These phenomena are also relevant

for micro- and nano-fabrication and for microreactors,

because multiphase flow can also be used for separation

and encapsulation of desired products. The development

of such reactors requires the aid of polymer materials

science, which will yield optimal fluids, substrates,

surface treatment, and active devices.

For More Information on this Topic

S.D. Hudson, K.B. Migler, J. Pathak, J.F. Douglas,

J.G. Hagedorn (ITL); N. Martys (BFRL)

Figure 4: Pearl necklace arrangement of PDMS drops

in a confined 5% mass fraction PDMS/PIB emulsion flowing

in the horizontal direction at a shear rate of 4.25 s–1,

viewed normal to the confining planes, which are spaced

36 μm apart.

Technical Highlights
8

Pore Size Distributions in Low-k Dielectric Thin Films

from X-ray Porosimetry

NIST is working to provide the semiconductor

industry with detailed information on the nanoscopic

pore size distribution of porous thin films destined

as low-k dielectric materials for the next generation

of integrated circuits. The electronics industry has

chosen the introduction of nanometer scale pores

into interlayer dielectric films as the method of

lowering the effective dielectric constant. While these

modifications change the dielectric constant favorably,

other important parameters such as physical strength

and barrier properties will also change, often in an

unfavorable way. A new method has been developed

to calculate the pore size distribution from x-ray

reflectivity measurements on thin films in a controlled

environment of solvent vapor.

The rapid and sustained advances in ultra-large-scale

integrated circuit performance have been driven,

to a large extent, by miniaturization of the circuitry.

At these nanoscopic sizes, interlayers with extremely

low dielectric constants (low-k) are imperative to reduce

cross-talk and to increase processor speed. While the

candidate materials differ in their base chemistries, a

common theme emerges in the push to develop low-k

dielectric materials: nano-scale porosity must be

introduced in a controlled manner to further reduce the

dielectric constant. Techniques are needed to accurately

and non-invasively characterize the porosity in these

films while attached on a silicon substrate.

Capillary porosimetry is a prime candidate to

measure the pore size distribution (PSD) of the

nanoporous films. Bulk materials have been

characterized in this manner by measurement of the

mass gain of the material when exposed to a controlled

pressure of solvent vapor. As the pressure of the probe

solvent increases, pores become filled hierarchically by

size as is described by the appropriate thermodynamic

analysis such as the Kelvin equation:

that an equilibrium amount of adsorption occurs. The

value of P/Po can be varied either by mixing volumes of

solvent saturated and dry air at a constant temperature,

or by blanketing the sample in air that has reached

solvent saturation at a low temperature and increasing

the temperature of the thin film. Under such conditions,

a standard XR scan gives accurate values of the total

density that is a combination of wall density and solvent

filled pores. The mass uptake as a function of partial

pressure is calculated from these results.

As an example, the reflectivity data from the porous

hydrogen silsesquioxane (HSQ) and the silica xerogel

films are shown in Figure 1. Each of the two samples

has several data sets plotted together to show the effect

of solvent adsorption. A critical edge is clearly visible at

low qz values as the sharp drop in log(Reflectivity) from

the initially flat reflectivity curve. In Figure 1, four curves

are shown for each sample, varying from the sample

exposed to dry air (left most curve) to sample in

saturated toluene vapor (right most curve). There is a

progression of the critical edge to higher qz as the vapor

pressure increases, due to the increased electron density

of the film as the smaller pores become saturated with

liquid toluene.

ln( / )

2

RT P P0

V

r m − γ = Figure 1: XR curves of a porous organosilsesquioxane

(XLK) and xerogel films under controlled partial

toluene vapor pressure.

At P/Po = 1, toluene will condense in all of the

accessible pores or open pores by definition, so the

uptake at saturation, Wo, is a measure of the porosity.

It should be emphasized that this porosity only reflects

those pores that the toluene can infiltrate. There may

also be closed pores not accessible to toluene vapor

and therefore not reflected in the XR porosity.

Therefore, a matrix density that is a combination of

dense wall material and inaccessible closed pores can

be calculated.

where the pore radius, r, can be calculated from

the partial solvent vapor pressure, P/Po, known

thermodynamic properties of the solvent such as

surface tension, γ, and molar volume, Vm, temperature,

T, and gas constant, R.

X-ray reflectivity (XR) has been extensively used

in the Polymers Division to measure the thickness and

density of 1 μm nanoporous thin films. A method of

x-ray porosimetry (XRP) has been developed to create

a controlled solvent environment around the thin film so

Technical Highlights
9

Figure 2 presents the adsorption/desorption data

for a porous methyl silsesquioxane (MSQ) spin-on

glass (SOG) film in which P/Po is varied through the

substrate temperature. The solid lines are cubic spline

fits through the data and accurately mimic the shape

of the curves. The data points have considerably less

scatter than the data in which the isothermal technique

is employed. The hysteresis loop is very well defined

with data outside of the loop coinciding accurately.

If the principle of temperature–pressure equivalency is

valid, the temperature control method clearly increases

the accuracy of the measurement.

a special substrate, such as the piezoelectric surfaces

required for both the quartz crystal microbalance

and surface acoustic waves techniques. XRP can

be done on any smooth substrate, including the Si

wafers used in the semiconductor industry. In many

ways, XRP is similar and complimentary to optical

methods such as ellipsometric porosimetry (EP).

However, the EP analysis requires knowledge of

the optical constants, for both the matrix and the

adsorbate. With EP it is also necessary to invoke

the additional assumption that the polarizabilities

are additive. XRP does not require these additional

assumptions.

Another potential advantage of XRP is the ability

to quantify not only the average film density, but also

the density profile normal to the film surface. X-ray

reflectivity has been used to extract non-uniform

density profiles in a series of low-k films. It may be

possible to use XRP to extract pore size distributions

as a function of depth into film. To prevent dielectric

breakdown, it is desirable to have low porosity or very

small pores near the surfaces with the majority of the

porosity localized in the center of the thin film. XRP

could prove to be very useful for characterizing these

types of structures.

“The SANS/SXR measurements have become a key

metric in our low-k dielectric materials characterization

and screening process.”

Dr. Jeffrey Wetzel

Manager

Low-k Materials Technology

International SEMATECH

“The NIST x-ray reflectivity program is useful,

perhaps even critical, to the industry.”

Dr. Abner Bello

Technical Staff Member

Defect and Thin Film Characterization

Laboratory Applied Materials, Inc.

For More Information on this Topic

B.J. Bauer, W.L. Wu (Polymers Division, NIST)

Hae-Jeong Lee, Christopher L. Soles, Da-wei Liu,

Barry J. Bauer and Wen-li Wu, “Pore size distributions

in low-k dielectric thin films from X-ray porosimetry,”

Journal of Polymer Science, Polymer Physics Edition,

(in press).

Figure 2: XR toluene vapor adsorption data from MSQ

SOG films by varying the substrate temperature.

The pore size distribution can be calculated by

use of the Kelvin equation and other thermodynamic

considerations from a point-by-point differentiation,

as shown in Figure 3.

Figure 3: PSD of MSQ SOG films by varying the substrate

temperature (where AU = arbitrary units).

There are several advantages of XRP over other

techniques to determine pore size in ultrathin films.

Some methods require that the film be deposited on

Technical Highlights
10

Direct Measurement of the Reaction Front in

Chemically Amplified Photoresists

The continual device performance increases by the

semiconductor industry has been largely driven by

the fabrication of smaller structures with lithography.

As feature sizes approach sub-100 nm, the

photolithographic process must be controlled with

tolerances of (2 to 5) nm, dimensions comparable

to the molecular size of the polymer chains in the

photoresist imaging material. New experimental

methods are needed to measure transport and

materials science phenomena over nanometer

length scales to provide critically needed data for

the understanding, design, and control of new

lithographic materials and processes. In collaboration

with IBM and the University of Texas, we directly

measured the spatial evolution of a reaction front,

within a photoresist, with nanometer resolution

using neutron and x-ray reflectometry and a

deuterium-labeled photoresist polymer.

The semiconductor industry is rapidly approaching

 the need to fabricate sub-100 nm structures to

continue performance increases in integrated circuits.

Photolithography remains the enabling technology for

the fabrication of integrated circuit patterns. Although

industry is able to commercially produce 130 nm

features, lithographic materials and processes are

not fully available for the production of sub-100 nm

structures. New materials must be able to produce

structures with dimensional tolerances of (2 to 5) nm,

dimensions near the size of the polymer chain molecules

in the imaging layer.

1 and 2. The patterns are generated in the resist by

exposure to UV radiation through a mask. In the

exposed areas, the PAG decomposes forming an acid

species. Upon baking, the acid diffuses and catalyzes

a deprotection reaction rendering the insoluble resist

soluble in a developer. The soluble regions are then

removed with the aqueous base developer. Control

over this process is dominated by the events in the

transitional region between exposed and unexposed

areas of the photoresist.

Figure 1: At left, SEM image of a lithographically

fabricated structure with a nominal critical dimension of

150 nm and 300 nm pitch. At right, schematic illustration

of patterning through a mask to create the structure.

Current imaging layers, chemically amplified

photoresists, are multi-component materials consisting

of a polymer resin initially insoluble in an aqueous base

developer solution, a photoacid generator (PAG), and

other additives. A schematic diagram of the fabrication

process and an example structure are shown in Figures

Figure 2: Schematic diagram of the reaction-diffusion

process in chemically amplified photoresists. The

transitional region between exposed and unexposed

regions is particularly important for critical dimension

and roughness control.

The initial development of chemically amplified

photoresists was a key technological breakthrough

furthering the continued use of optical photolithography

for the fabrication of sub-micrometer features. The

importance of chemically amplified photoresist concepts

is illustrated by the industry-wide use of these materials

in the fabrication of state-of-the-art devices today and

into the foreseeable future. With the imminent need

for sub-100 nm feature sizes, nanometer level control

over the spatial evolution of the deprotection reaction

front and the subsequent development steps is needed.

The current level of understanding of the acid-catalyzed

reaction-diffusion process is not sufficiently detailed to

achieve this goal.

Technical Highlights
11

To meet the need for spatially detailed data, we have

developed, in collaboration with the IBM T. J. Watson

Research Center and the University of Texas at Austin,

an experimental methodology to measure directly the

spatial evolution of the deprotection reaction front

through each processing step. By using model

photoresist polymers with a deuterated protection

group, neutron and x-ray reflectivity (NR, XR)

measurements are able to follow the compositional

and density profiles of the reaction-diffusion process

in an idealized transitional region in a bilayer film stack.

Neutron contrast with the reaction is possible because

the reaction products involving the deuterated protection

group are volatile as illustrated in Figure 3.

control over the fabrication of sub-100 nm structures.

In addition, the strategy developed here is general and

can be adapted for the study of candidate photoresist

materials being developed for future applications.

Figure 4: A) schematic diagram of the processing steps

including the application of each film layer, exposure to UV

radiation, a post-exposure bake (PEB) and development.

B) and D) show the NR data and compositional depth

profile and C) and E) show the XR data and density

depth profiles from each step.

For More Information on this Topic

E.K. Lin, C.L. Soles, R.L. Jones, J.L. Lenhart,

W.L. Wu (Polymers Division, NIST); S.K. Satija

(NCNR, NIST)

E.K. Lin, C.L. Soles, D.L. Goldfarb, B.C. Trinque,

S.D. Burns, R.L. Jones, J.L. Lenhart, M. Angelopoulos,

C.G. Willson, S.K. Satija, and W.L Wu, “Direct

Measurement of the Reaction Front in Chemically

Amplified Photoresists,” Science, 297, 372, (2002).

Figure 3: General deprotection reaction in a chemically

amplified photoresist. Deuterated molecular parts

with strong contrast to neutrons are shown in red.

PHOSt = polyhydroxystyrene, PBOCSt = poly

p-tert-butoxycarboxystyrene.

The NR and XR results from a series of bilayer

samples are shown in Figure 4. NR and XR

measurements were taken after each processing

step from the spin-coating of each film layer through

exposure and bake to the dissolution of the upper layer

and any deprotected polymer. The data show that the

deprotection reaction front broadens with time within

the photoresist. The initial interfacial width was

approximately 4 nm wide whereas the reaction front

was nearly 20 nm wide. Upon development, the data

show that the developed film remained sharply defined

with a surface roughness of approximately 4 nm as

well. Although the reaction front was much wider

than the final interfacial width, the selectivity of the

dissolution process allows for the fabrication of

well-defined nanostructures with diffusive

transport mechanisms.

The spatial detail afforded by the developed

methodology can play an important role in not only the

qualitative description of the reaction-diffusion process,

but also with the quantitative determination of physical

parameters and changes in any physical or chemical

properties over the nanometer length scales required for

“[This work] opens a window of opportunity to

construct structure-property relationships between

chemical transport mechanisms and ultimate resist

resolution. It may also lead to insights into the ultimate,

intrinsic resolution limits and critical dimension control

of polymer-based imaging materials.”

E. Reichmanis and O. Nalamasu

Bell Labs, Lucent Technologies,

Science, 297, 349, (2002)

Technical Highlights
12

Metrologies for Tissue Engineering

Tissue engineering represents a new paradigm

in medicine by seeking to regenerate missing or

damaged tissue. Developing, manufacturing, and

regulating tissue-engineered medical products

requires proving the safety and efficacy of these

complex devices. This presents a significant

measurement challenge involving qualification

of materials, cells, and delivery methods.

Tissue engineering is a rapidly growing field that

 presents a host of new measurement problems for

producers and regulators. Tissue engineered medical

products are typically hybrid devices that incorporate

materials and cells in order to regenerate damaged

tissue. The safety and efficacy of both materials and

cells, as well as their interactions, must be qualified

in order for these to gain acceptance, and we are

developing a host of in vitro tests to assist in this

process.

Events at the cell–material interface determine the

performance of these devices, but the complexity of

the interactions has prevented development of a more

rational approach to tissue engineering. In the Polymers

Division, we are extending the established program in

combinatorial methods to biomaterial interfaces. This

will permit rapid screening of material variables and

evaluation of their effects on cells.

The extracellular matrix (ECM) to which cells

adhere can initiate healing, direct cell migration, control

cell cycle progression, and determine cell differentiation.

The scientific community is just beginning to understand

intracellular signaling networks, but it is clear that

external stimuli participate in the cycle of cell activity.

The challenge of tissue engineering is to control cellular

behavior through the rational design of materials and

culturing conditions. The industry is years away from

meeting this challenge due, in part, to a void in the

measurement infrastructure at the cell-biomaterial

interface. Efforts within the Polymers Division to fill this

void fall under three general topics: developing material

libraries, expanding imaging capabilities, and managing

and analyzing data.

Developing Material Libraries

We are developing a three-tiered material library

for investigating cell-material interactions; each tier

represents an increased level of complexity. The first

tier comprises polymeric material surfaces designed

to mimic bulk material interfaces currently found in

industrial applications. The second tier contains

material surfaces designed to mimic the ECM through

incorporation of cell-signaling molecules such as

peptides and oligosaccharides. While the first two

tiers describe pseudo-two-dimensional phenomena,

the third tier includes three-dimensional materials.

Current industrial applications, and those of the

near future, rely on relatively simple materials such as

poly(lactic acid) and poly(dimethylsiloxane). Even so,

variables such as composition and processing conditions

can drastically affect physical properties. Particular

properties of interest include: nanometer- and

micrometer-scale topography, hydrophilicity, charge,

and mechanical rigidity. The Polymers Division has

established methods for preparing gradient material

surfaces encompassing this parameter space. As these

methods are transferred to biomaterial systems, the first

tier of our library will develop. From this tier, we will

identify and develop SRMs that will assist industry in

developing products, assessing quality control, and

gaining regulatory approval.

The next generation of tissue engineered medical

products will incorporate cell-signaling molecules such

as peptides and oligosaccharides. These materials will

be engineered to interact with specific receptors and

elicit selective cellular responses. Doing so requires

fine-tuning the stimuli offered to cells by presenting

appropriate combinations of signaling molecules. The

cells then receive signals capable of initiating more

complex cascades ultimately leading to the desired

cellular response. This chain of events would emulate

that which occurs during natural tissue formation.

A high-throughput approach is uniquely qualified to

characterize this complex, multi-dimensional space of

ECM cues and cellular responses. As methods for

preparing such materials are developed, the second

tier of our library will emerge. From this tier, we will

contribute to the general understanding of intracellular

signaling networks, groundwork necessary for the

development of new tissue engineered medical products.

Real tissues are inherently three-dimensional and

realistic measurement tools will need to be as well. We

are currently developing three-dimensional materials and

Figure 1: Cell adhesion to a polymer blend.

Technical Highlights
13

associated measurement methods to begin a metrology

system complementary to the two-dimensional systems.

Similar material issues will be faced with the added

complication of three-dimensional architecture and its

influence on cellular response. Such is the scope of

the third tier of our library. In addition, other issues

related to tissue engineered medical products will

be investigated with a goal of creating necessary

measurement capabilities. The devices being developed

by tissue engineering companies have multiple

requirements in order for them to be safe and effective.

They have stringent mechanical requirements which

depend on the tissue being engineered; they must allow

infiltration by the necessary cells; and the inflammatory

responses they evoke must be minimized. Toward this

end, we are developing in vitro testing protocols for

these performance requirements that will be used in

screening tissue engineered medical products.

Expanding Imaging Capabilities

The described three-tiered material library only

has value if cell response across the library can be

well characterized. A host of strategies exist for

characterizing cell response; many fall beyond the scope

of the Polymers Division and are pursued through

external collaborators. On site, we have targeted visual

imaging of cells through conventional microscopy,

fluorescence microscopy, confocal microscopy, and

optical coherence tomography (OCT). The OCT image

below shows pores in red and tissue scaffolding in blue.

prepared from a blend of two polymers. The film might

consist of a composition gradient along one axis and

might be annealed (processed) under a temperature

gradient orthogonal to the composition gradient.

Characterization of this film would begin by mapping

processing conditions, i.e., composition and annealing

temperature as a function of position. An array of AFM

images may be taken to map the surface topography.

An array of contact angles may be measured to map

the surface energy. Finally, an array of images would

be collected and analyzed to measure cell response.

In order to identify correlations, each of these data

maps must be in alignment.

Once data maps are aligned, a rigorous statistical

analysis is necessary to quantify correlations and make

meaningful hypotheses of causality. Material parameters

can be analyzed following traditional engineering

statistics. Data from living organisms requires an

alternative strategy. Whether measuring general,

morphological parameters such as cell area upon

spreading or more specific parameters such as the

regulation of gene expression, the cell response will

fall within a distribution defined by the cell line. Unlike

measured material parameters, variations from the

mean may not be random, so reducing data to a

mean and standard deviation can result in a loss of

critical information.

The very nature of the combinatorial methodology

will require that image acquisition be well documented

and unbiased in order to correlate cell response to

material properties. We envision a streamlined process

where cells are seeded onto a material, incubated,

fixed, and stained following an established experimental

protocol. An array of images would be collected and the

entire surface mapped. Images would then be reduced

to quantitative measures of cell response.

Managing and Analyzing Data

The task of accurately overlaying data maps presents

a significant challenge. For example, a thin film could be

Figure 2: OCT image of a tissue engineering scaffold.

As such, images of cells are collected, analyzed,

and reported in a manner that maintains the fullest

description of a population distribution. Furthermore,

when investigating the cell response to a variety

of material scaffolds, evaluations are based on a

statistical comparison between corresponding

cell populations.

For More Information on this Topic

N. Washburn, S. Kennedy, E. Amis

Niklason, L.E., Langer, R., “Prospects for

Organ and Tissue Replacement,” JAMA,

February 7, 2001.

Figure 3: An extreme example of two population

distributions that are clearly different, yet they have the

same average and standard deviation.

Technical Highlights
14

NIST Combinatorial Methods Center

The NIST Combinatorial Methods Center (NCMC)

was formally established in January 2002 to

provide information and expertise on combinatorial

methods to a wide range of industrial, academic

and government institutions interested in acquiring

combinatorial and high-throughput capabilities suited

for materials research. The NCMC functions through

two complimentary efforts. 1) A research program

geared towards the development of techniques and

instrumentation for the fabrication and analysis of

novel combinatorial libraries. This research centers

on novel gradient combi methods, where the NCMC

has recognized expertise. 2) An outreach program

designed to gauge industrial needs in combi research

and effectively disseminate data, instrumentation

design, best practices and protocols, and other

information relevant to combi techniques.

Combinatorial techniques offer a highly parallel,

 automated, and often miniaturized route for

experimentation that allows hundreds or thousand of

specimens to be fabricated and analyzed in a rapid and

efficient fashion. Such techniques provide opportunities

to significantly boost productivity, increase the scope

of parameter-space exploration, and enhance the

understanding of complex systems in a variety of

scientific and technological disciplines. Indeed, in recent

years the unmitigated success of combinatorial and

high-throughput methods in the pharmaceutical industry

and the genomics effort has spurred researchers in the

materials science and chemical industries to reconsider

their reliance on traditional “one-at-a-time” experimental

approaches to product and knowledge discovery.

However, several challenges impede the successful

adaptation of combinatorial methods in these arenas. For

example, pharmaceutical combi models, which emphasize

product discovery, often do not provide insight into the

structure/property/processing relationships that are

central to materials research. In addition, techniques and

instrumentation explicitly suited to the high-throughput

fabrication and analysis of combinatorial libraries of

interest to materials scientists need to be developed.

Moreover, many institutions interested in acquiring

combinatorial methods require information on how to

incorporate such strategies into their research program.

In response to these technical and educational

needs, the NIST Combinatorial Methods Center

(NCMC) was formally established in January 2002.

A NIST-wide effort centered in the Polymers Division,

the NCMC includes contributions from throughout

MSEL and several other laboratories including Building

and Fire Research, Physics, and Chemical Science

and Technology Laboratories. The NCMC’s mission

is twofold. As a research program focused upon the

creation of novel specimen libraries and instrumentation,

the NCMC advances the state-of-the-art in combinatorial

methods geared towards materials research and discovery.

A complimentary effort is an outreach program, which

serves to disseminate NCMC research products,

instrument design, best protocols and practices, and

other information relevant to the combi method. This

organization also provides an effective means by which

industrial needs are gauged.

NCMC combinatorial methods research is rooted in

the so-called gradient approach. The core of gradient

combi is the gradient specimen. These samples

continuously vary in one property (e.g., film thickness)

along a spatial coordinate over a prescribed range.

By arranging two such gradients (e.g., thickness and

temperature) in an orthogonal manner, a gradient library

is created that exhibits every possible combination of

properties within the scope of the constituent gradient

specimens. Gradient libraries are particularly useful to

materials scientists because they offer a convenient and

thorough way in which to map parameter space. In

addition, gradient libraries are especially amenable to

examination via microscopy and microanalysis, which

facilitates the illumination of structure–property

relationships. Finally, as opposed to many robotics-oriented

discrete approaches, gradient techniques can offer a

cost-effective way of performing combinatorial studies,

making them attractive to a wider range of institutions.

This year, several new techniques were added to the NCMC

repertoire. New instrumentation for generating gradients

in ultraviolet-radiation (UV) exposure was central to this

effort. Here, a UV slit-source is accelerated across a planar

specimen. When this source is held in close proximity (<

5 mm) to the sample, UV-generated ozone can chemically

modify self-assembled monolayer (SAM) treated sample

surfaces resulting in a gradient in surface energy and/or

chemical functionality. Depending upon the SAM employed,

such surface energy gradients can span 70° in water contact

angle. Larger source/sample distances are effective in

producing gradients in light-induced crosslinking,

polymerization, and degradation. Since the degree of

UV exposure is controlled through stage motion, this

instrument is particularly versatile. Gradient profile,

depth and steepness are easily tuned for a wide range

of applications. In another new technique, gradients in

the height of topographic surface features are created.

Here, topographic gratings are lithographically etched

Figure 1: Scheme 1 —

Gradient combinatorial library.

As they are the

basic unit of gradient

libraries, many NCMC

research efforts

concentrate upon the

development of novel

gradient specimens

and processes, with

polymer science being

a focus in recent years.

Methods for producing

gradients in film

thickness, composition

and temperature

formed the basis of

previous NCMC studies.

Technical Highlights
15

into wedges of silsesquioxane “spin-on” oxides created

via flow-coating. The resulting patterns, with heights

ranging from (30 to 150) nm, provide a combi strategy

for examining topography-mediated templating of film

properties, making them useful for the development of

thin-film optoelectronic devices and MEMS.

NCMC research also generates new techniques and

instrumentation for the high-throughput measurement

of materials properties. This year, efforts concentrated on

combinatorial methods for evaluating mechanical properties

and adhesion. Gradient film libraries mounted on

deformable copper grids enable combinatorial examination

of polymer failure mechanisms. In another technique,

libraries prepared on rubbery polydimethylsiloxane supports

allow high-throughput modulus measurements. Recently

completed instrumentation facilitates sophisticated

combinatorial measurements of adhesion via the Johnson–

Kendall–Roberts (JKR) approach using micro-lens arrays.

In addition, methods for performing combinatorial tests

of interfacial fracture were developed in conjunction

with a modeling effort that guides interpretation of

experimental data.

Due to these and previous research efforts (some

of which are detailed in this report), the NCMC has

established a widely-recognized expertise in gradient

combinatorial materials science. This impact is

demonstrated by the success of the NCMC outreach

program, described below.

NCMC Outreach

The foundation of NCMC outreach is a membership

program that invites industrial, academic, and government

institutions to participate in a consortium designed to

facilitate the advancement of combinatorial materials

research. This program serves as a conduit through

which NCMC research products are disseminated

and industrial needs are gauged. Since the NCMC

emphasizes relationships and collaboration that do

not involve proprietary information, Center/member

and member/member communication is maximized.

However, collaborations that address specific industrial

problems are established when necessary.

The NCMC has currently attracted 11 members (see

table below), in part due to an extensive dissemination and

recruiting effort that culminated in the inaugural NCMC

conference held in San Diego, CA in January 2002.

Members are served through several routes. Foremost

among these is a series of tri-annual members’ meetings

that showcase NCMC technical advances and protocols,

distribute information on research conducted at NIST and

elsewhere of relevance to combinatorial methods, and

provide a forum in which current issues and needs in

combinatorial and high-throughput research are discussed.

The first NCMC members meeting, held on April 26,

2002, was attended by over 20 representatives from 8

industrial institutions. Entitled, “Library Design and

Calibration: What you need to know and do before you

look for hits,” this meeting involved a variety of activities.

Technical presentations detailed the design of combinatorial

experiments using the gradient technique and methods for

calibrating gradient libraries. The importance of these

processes in combinatorial research was demonstrated

through a case study that illustrated how calibration and

design principles work in an actual research program.

An NCMC staff-led discussion focused on combinatorial

strategies for multicomponent formulations research and

management of the massive amounts of data combinatorial

studies necessarily produce. Laboratory demonstrations

designed to provide practical first-hand knowledge about

NCMC instrumentation and gradient techniques focused

upon flow coating, composition and surface energy

gradients, automated hot-stage optical microscopy,

adhesion measurement instrumentation, infrared-imaging,

and combinatorial mechanical testing. The second NCMC

meeting, “Adhesion and Mechanical Properties,” is slated

for October 2002.

This year has also seen numerous visits to NCMC

facilities by member parties. For example, both Rhodia

and the Air Force Research Laboratory sent staff to

work alongside NCMC scientists on combinatorial

projects. This type of interaction is especially useful to

institutions that are new to combinatorial research and

its effective implementation.

The new NCMC website (http://www.nist.gov/combi)

provides information on the center and its activities, research

publications from the NCMC and selected sources in the

public domain, instrument schematics and specifications,

and automation and analysis software. Additional resources,

including browsable combinatorial data libraries, are also

in development.

“Combinatorial methods offer the

possibility of accelerating industrial

materials research. The NCMC

is well suited to drive this new

technology because of their excellent

work in high-throughput application

testing. . .and addressing industrial

needs. Industry will benefit by getting

started in combi earlier.”

Wolfgang Schrof

Polymer Physicist, BASF (NCMC Member)

For More Information on this Topic

C. Davis, M. Fasolka, A. Karim, E. Amis (Polymers

Division, NIST)

Figure 2: NCMC Members. Visit the NCMC website at http://www.nist.gov/combi

Technical Highlights
16
17

Advanced Manufacturing Methods

An increasingly competitive manufacturing

environment drives the search for new materials and

processing techniques to make them. In most cases,

materials processing steps determine the microstructure

and performance of the material while manufacturing

costs determine price. Industry needs measurement

methods, standards, and data that will help monitor,

control, and improve processing methods. These tools

are also needed to help understand materials processing

and to develop new processing methods and materials

with enhanced properties. This is as true for highly

developed, well-established industries as it is for

rapidly growing or emerging industries. It is also true

for all types of materials, processes, and products.

The industrial competitiveness of the United States

depends on U.S. manufacturers’ ability to use the

measurement tools to develop and advance their

manufacturing methods. In many cases, the needed

tools are generic and their impact would be greatly

enhanced if they became industry wide standards.

Therefore, MSEL is working to develop measurement

methods and standards to enable industry to achieve

these goals. This work is often being conducted in

close collaboration with industry through consortia and

standards organizations. The close working relationship

developed with industry through these organizations not

only ensures the relevance of the research projects, but

also promotes an efficient and timely transfer of research

information to industry for implementation. Since

different materials and industries frequently have similar

measurements needs, and most industrial products have

multiple materials components, this program covers the

processing of ceramics, metals, and polymers.

Research in the Ceramics Division focuses on

development of test methods for the assessment of

contact damage and wear, development of test methods

and predictive models for evaluation of mechanical

properties at elevated temperatures, and development

of models for prediction of coating properties and

performance. One project focuses on low temperature

co-fired ceramics (LTCC), a manufacturing method

being developed largely for portable wireless modules

because it promises to allow for a reduction in the size

and cost of modules used in high-frequency applications

while improving performance. Because dimensional

tolerances are critical in this process, accurate

measurements and predictive models of dimensional

changes during sintering are necessary for the

commercialization of LTCC modules. Measurement

methods and predictive models for the overall shrinkage

and the local variations in sintering near vias and

interconnects are being developed.

Projects in the Metallurgy Division cover

several processing and measurement methods. The

performance of metallic components in products is

strongly dependent on processing conditions that

determine microstructural features, such as grain size

and shape, texture, the distribution of crystalline phases,

macro- and microsegregation, and defect structure and

distribution. Expertise is applied from a wide range of

disciplines, including thermodynamics, electrochemistry,

fluid mechanics, diffusion, x-ray, and thermal analysis,

to develop measurement methods and understand the

influence of processing steps for industries as diverse as

automotive, aerospace, coatings, and microelectronics.

Rapidly growing and emerging industries such as

biotechnology and nanotechnology are dependent

upon the development of new advanced manufacturing

methods that can produce metallic components with

the desired characteristics and performance. Current

projects focus on measurements and predictive models

needed by industry to design improved processing

methods, provide better process control, develop

improved alloy and coating properties, and reduce

costs. Important processing problems being addressed

include melting and solidification of welds, solidification

of single crystals, powder production and consolidation,

and coating production by thermal spray and

electrodeposition.

Polymeric materials have become ubiquitous in the

modern economy because of their ease of processing.

However, these materials can exhibit complex and

sometimes catastrophic responses to the forces imposed

during manufacturing, thereby limiting processing rates

and the ability to predict ultimate properties. The focus

of the Polymers Division is directed towards microscale

processing, modeling of processing instabilities, and

on-line process monitoring of polymeric materials.

Our unique extrusion visualization facility combines

in-line microscopy and light scattering for the study of

polymer blends, extrusion instabilities, and the action of

additives. Current applications focus on understanding

and controlling the “sharkskin instability” in polymer

extrusion and observation of the dielectric properties

of polymer nanocomposites. 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.

Contact: Kalman Migler

Program Overview
18

Control of Extrusion Instabilities

Polymeric materials have become ubiquitous in the

modern economy because they are comparatively

easy to process. However, polymeric materials exhibit

complex and sometimes catastrophic response to

the forces imposed on them during manufacturing.

These instabilities prevent or retard processing. In

this project we seek new measurement technologies

to understand and control processing instabilities.

Kalman Migler

The manufacturability of important classes of

 polymers is limited by processing instabilities. Our

goal is to fully understand the well-known instability

(sharkskin) via development of new measurement

technology that can unravel the relationship between

polymer rheology, flow boundary conditions, and the

resulting surface roughness. The output of the project

will be to provide suppliers and users with guidelines

for reducing this instability. This line-of-attack will then

serve as a model for more complex processing operations

in which flow instabilities hamper large-scale production.

Our work published over the previous two years

provided conclusive evidence regarding the nature of

the flow conditions that exist during sharkskin melt

fracture of polyethylene. We also provided the first

direct evidence of how fluoropolymer additives modify

the flow boundary condition so as to eliminate sharkskin.

However, the fluoropolymer additives are only effective

when they efficiently migrate to the wall where they

coat it, producing a thin fluoropolymer layer. There has

been virtually no research to understand this complex

phenomenon; in fact, reasonable theoretical arguments

anticipate that the dispersed fluoropolymer droplets

should migrate away from the wall. Understanding the

mechanism of fluoropolymer deposition at the wall will

optimize future additives and will provide insight into other

manufacturing operations where these effects may occur.

Our approach is to conduct in situ measurements of the

coating process by starting with pure polyethylene and

monitoring the sharkskin. We then mix approximately

0.1% mass fraction fluoropolymer into the polyethylene

and correlate the instantaneous thickness of fluoropolymer

at the wall with the state of sharkskin and the decreasing

pressure required to drive the polymer through the

extrusion tube.

We have chosen an optical technique based on Total

Internal Reflection (TIR), which is sensitive to the

presence of a thin layer of fluoropolymer at the sapphire

wall (see Figure 1). The principle is that a critical angle,

α, exists when light travels from a material with a high

index of refraction to one with a low index of refraction

(such as occurs in a swimming pool.)

We take advantage of the differing indices of refraction

of the three materials: sapphire, polyethylene (PE) and

fluoropolymer (polymer processing additive, PPA).

When the polyethylene is in intimate contact with the

wall (which causes sharkskin) the critical angle for TIR

is 53o. When fluoropolymer displaces the polyethylene

at the wall, the critical angle decreases.

Preliminary measurements indicate that a layer sensitivity

of 25 nm may be achievable and that this technique may

have application for a variety of extrusion instabilities

such as the spurt phenomenon.

Figure 1: Cross section of polymer extrusion tube also

showing the relevant angles of the optical reflections.

Figure 2: Reflectivity off the sapphire-polyethylene

interface (diamonds) and off the sapphire-fluoropolymer

interface (triangles).

Contributors and Collaborators

K. Migler; Dow Chemical, 3M Chemical Company,

Dupont-Dow Elastomers, McMaster University,

University of Minnesota

Advanced Manufacturing Methods
19

Process Monitoring of Polymer/Clay Nanocomposites

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, to control the process, and to predict

performance of the final product. In this project, we

are developing measurement techniques based on

optical, dielectric, rheological, and ultrasonics

techniques. NIST has filled an industry need by

designing and constructing process sensors and by

collaborating with industry partners in the application

of new sensor technology to process monitoring.

Anthony J. Bur

The state of the microstructure that forms during

 the compounding and mixing of clay and polymer is

the primary factor determining composite performance.

Current practice is to analyze the processed product offline using transmission electron microscopy (TEM) and

x-ray scattering to determine the extent of aggregate,

intercalated, or exfoliated microstructure. In order to

minimize the need for off-line measurements, we are

developing on-line instrumentation that will yield

real-time microstructure information using dielectric,

rheology, and light transmission measurements. On-line

data can provide a basis for developing R&D processing

strategies that compounders can use to set process

parameters that yield targeted product microstructure.

Our approach to determining microstructure using

on-line instrumentation is to correlate real-time

observations with TEM, x-ray, and small angle

neutron scattering (SANS) observations.

In the first phase of this project, real-time dielectric

measurements were made using a ring-shaped ceramic

dielectric cell that has interdigitated electrodes deposited

on the inside surface of the ring. As resin flows through

the ring, an electric fringing field intercepts the resin and

the measured in-phase and out-of-phase currents are

used to calculate the real and imaginary parts of the

dielectric constant. Measurements carried out over a

range of frequency from 500 Hz to 100 kHz yield

dynamic information that characterize the electrical

relaxation times of the composite.

Real-time dielectric measurements on polyethyleneethyl vinyl acetate co-polymer (PE-EVA) mixed with

organo modified clays reveal a correlation between

microstructure and the dispersion in dielectric data as a

function of frequency. In Figure 1, the dispersion is seen

in the plot of the imaginary part of the dielectric constant

versus the real part. In this plot, the DC conductivity has

been subtracted out of the imaginary part in order to

reveal the relaxation dynamics of the composite at higher

These data are providing the platform for a

collaboration with Chemical ElectroPhysics Corporation

to develop a new dielectric slit die sensor with capability

to measure rheological, optical transmission, and

dielectric properties in real-time. The full package of

data from this sensor will be the basis for designating

the microstructure of the compounded composite.

Reference: A.J. Bur, S.C. Roth and M. McBrearty,

Rev. Sci. Instrum., 73, p. 2097, (2002).

Contributors and Collaborators

A.J. Bur, S.C. Roth, S.D. Hudson, C.R. Snyder,

D.L. VanderHart (Polymers Division, NIST);

C.J. Glinka, D. Ho (NIST Center for Neutron

Research); J. Gilman (Fire Research Division, NIST);

M. McBrearty (Chemical ElectroPhysics Corporation,

Hockessin, DE)

Figure 1: The imaginary versus real part of the dielectric

constant is shown for PE-EVA copolymer compounded with

two clays, 15A and 30B at 150oC. X-ray measurements

confirm that PE-EVA/15A clay is in the intercalated state

and PE-EVA/30B clay is in the aggregate state. The

broad dispersion seen in the 15A composite is due to

intercalated microstructure.

frequencies. Because these measurements are made

in the melt at 150oC, ionic conductivity dominates the

dispersion effects. This dispersion has its origins in

the layered structure of the intercalated microstructure.

The dielectric data in the figure are a direct result of the

presence of microstructure in the form of silicate layers

of smectite clay with organic polymer occupying the

space between layers. From an electrical point of view,

silicate layers interspersed with polymer resin behave as

a series of capacitances and resistances giving rise to

electrical relaxation dynamics having a broad distribution

of relaxation times. It is our hypothesis that the shape

and magnitude of this dispersion can be correlated with

the microstructure that is revealed in TEM and x-ray

observations.

Advanced Manufacturing Methods
20

Liquid Crystalline Nanostructures:

Phase Behavior and Processing

In the search for new materials, relationships between

molecular structure and material organization and

properties must be established. By microscopic

investigation of amphiphiles of novel molecular shape,

we identify their phase behavior and explore how

these materials can be aligned in the manufacture of

useful devices.

Steven D. Hudson and Hu Duan

Self-organized organic nanostructures with

 controlled optoelectronic properties that facilitate

ultra-high density nanopatterning represent one of the

challenges of molecular electronics. Similar materials

that yield pores of precise size and chemical and ionic

specificity represent another opportunity. To meet

these challenges, we measure phase behavior of these

materials and properties of their phase transitions.

Transmission electron microscopy provides key

information about the material organization. By

Fourier analysis of high-resolution lattice images,

the relative phase of diffracted beams is determined,

thus providing complementary information for

diffraction analyses.

This capability proved useful in the investigation

of novel dendrons, having a dipeptide head unit and

several aliphatic tail units. These molecules assemble

into a hexagonal columnar phase at low temperature

and, depending on molecular structure, either a cubic

or a weakly birefringent phase at high temperature.

Whereas some head units fail to form a special

organization, the dipeptide unit segregates by itself in

the center of the column, exhibiting a region of lower

density (Figure 1). Similar triply segregated structure

was observed in the cubic phase at high temperature.

Segregation of the head unit can be very important

and is responsible for high electronic carrier mobility

in columns comprising molecules with donor and

acceptor aromatic head groups.

Alignment of hexagonal columnar materials by

appropriate surface treatment and/or processing

procedure has been investigated. As mentioned

above, some of the dipeptide dendrons exhibit a weakly

birefringent phase at high temperature and a columnar

hexagonal phase at lower temperature. At still higher

temperature, the material forms an isotropic melt.

Cooling slowly from the melt produces 100 μm-sized

grains of the high temperature phase. Upon cooling

Figure 1: High resolution TEM image of the hexagonal

columnar phase of a dipeptide dendron. Inset upper left is

the corresponding electron diffraction pattern, exhibiting

(10), (11) and (20) reflections. Fourier analysis of the

image also exhibited these reflections and determined their

relative phase: – + +, whose combination results in the

“hollow” cylinder appearance of the image. The resulting

reconstructed image is inset bottom left.

The influence of shear flow on the order-disorder

transition of a polymeric material that exhibits

a hexagonal columnar phase was investigated.

Whereas weak shear stress at temperatures slightly

below the melting point align the microstructure,

larger stresses cause melting. Upon cessation of

shear, the hexagonal phase reforms by a row-nucleation

mechanism that produces macroscopic alignment of

the columns along the previous shear direction.

Phase transition phenomena, therefore, have a

significant influence over the alignment of the

material.

Contributors and Collaborators

S.D. Hudson, H. Duan (Polymers Division, NIST);

V. Percec (University of Pennsylvania); K.D. Singer

(Case Western Reserve University)

further, an epitaxial relationship between this phase

and the hexagonal columnar phase is observed.

Advanced Manufacturing Methods
21

Combinatorial Methods

The Combinatorial Methods Program develops

novel high-throughput measurement techniques and

combinatorial experimental strategies specifically geared

towards materials research. These tools enable the

industrial and research communities to rapidly acquire

and analyze physical and chemical data, thereby

accelerating the pace of materials discovery and

knowledge generation. By providing measurement

infrastructure, standards, and protocols, and expanding

existing capabilities relevant to combinatorial approaches,

the Combinatorial Methods Program lowers barriers to

the widespread industrial implementation of this new

R&D paradigm.

The Combinatorial Methods Program has adopted a

two-pronged strategy for meeting these goals. The first

of these is an active research and development program

designed to better tailor combinatorial methods for the

materials sciences and extend the state of the art in

combinatorial techniques. Measurement tools and

techniques are developed to prepare and characterize

combinatorial materials libraries, often by utilizing

miniaturization, parallel experimentation, and a high

degree of automation. A key concern in this effort is

the validation of these new approaches with respect

to traditional “one at a time” experimental strategies.

Accordingly, demonstrations of the applicability of

combinatorial methods to materials research problems

provide the scientific credibility needed to engender

wider acceptance of these techniques in the industrial

and academic sectors. In addition, the successful

adoption of the combinatorial approach involves a

highly developed “workflow” scheme. All aspects of

combinatorial research, from sample “library” design

and library preparation to high-throughput assay and

analysis, must be integrated through an informatics

framework which enables iterative refinement of

measurements and experimental aims. Combinatorial

Methods Program research projects give illustrations

of how these processes are implemented effectively in a

research setting.

NIST-wide research collaborations, facilitated by the

Combinatorial Methods Program, have produced a wide

range of new proficiencies in combinatorial techniques

which are detailed in a brochure, “Combinatorial

Methods at NIST” (NISTIR 6730), and online at

www.nist.gov/combi. Within MSEL, novel methods

for combinatorial library preparation are designed to

encompass variations of diverse physical and chemical

properties, such as composition, film thickness,

processing temperature, surface energy, chemical

functionality, UV-exposure, and topographic patterning

of organic and inorganic materials ranging from

polymers to nanocomposites to ceramics. In addition,

new instrumentation and techniques enable the

high-throughput measurements of adhesion, mechanical

properties, and failure mechanisms, among others.

The combinatorial effort extends to multiphase,

electronic, and magnetic materials, including biomaterials

assays. On-line data analysis tools, process control

methodology, and data archival methods are also being

developed as part of the Program’s informatics effort.

The second aspect of the Combinatorial Methods

Program is an outreach effort designed to facilitate

technology transfer with institutions interested in

acquiring combinatorial capabilities. The centerpiece

of this effort is the NIST Combinatorial Methods

Center (NCMC), an industry-university-government

consortium organized by MSEL that became operational

on January 23, 2002 via a kick-off meeting in San Diego.

Although it is still in the growth stage, the impact of

NCMC activities is readily apparent as 11 industrial

partners and the Air Force Research Lab have already

joined the NCMC membership program. The NCMC

facilitates direct interaction between NIST staff and

these industrial partners, and provides a conduit by

which Combinatorial Methods Program research

products, best practices and protocols, instrument

schematics and specifications, and other combinatorialrelated information can be effectively disseminated.

This outreach is mediated in large part by a series

of tri-annual workshops for NCMC members. The

first NCMC meeting, “Library Design and Calibration,”

was held on April 26, 2002 at NIST, and it provided

information essential to starting a combinatorial

research effort. The second meeting (October 2002)

will concentrate on combinatorial approaches to adhesion

and mechanical properties. Further information on NCMC

can be found on the website at www.nist.gov/combi.

Contact: Alamgir Karim

Program Overview
22

Combinatorial Adhesion and Failure

poly(dimethyl siloxane) films. The MCAT can also quantify

weak surface forces that dictate interface formation. For

these investigations, a modified geometry is used where

the microlens array is cast on a large curvature surface, or

macrolens (Figure 1(b)).

During the cooling of a laminated material (film/

substrate) system with an initial interfacial crack at a

stress-free edge, a further crack extension (debonding)

along the interface occurs at a critical temperature due

to the stress concentration near the crack tip. The Edge

Delamination Test (EDT) is based on this debonding

mechanism using the thermal stresses generated by the

mismatch of the coefficients of thermal expansion during

the cooling to cause separation of the film from the

substrate. Subsequently, the film-substrate adhesion

energy can be deduced from the failure map if the

internal stress-temperature relation of the film is known.

We use a test film that fails (debonds) due to the stress

generated by an over-coating polymer layer having a

thickness gradient. The bi-layer film is diced into a

square grid pattern to form an array of individual edge

delamination samples on the substrate (Figure 2).

To initiate debonding, the specimen is quenched into

a severe temperature gradient applied in the direction

orthogonal to the thickness gradient. Simulations

(not shown) predict interfacial debonding to occur in

regions exceeding a critical stress that depends on the

combination of local temperature and film thickness.

The red-line failure map of Figure 2 as a function

of temperature and film thickness is qualitatively in

agreement with these simulations. Such a reliability

map can be used to quantify the critical bond energy

of the thin film in the sub-micron thickness range for

semiconductor applications.

Figure 1: (a) Planar MCAT configuration; (b) Macrolens

with surface microlenses; (c) Time evolution of multilens

contact areas at fixed displacement. Color indicates time.

Figure 2: The experimental result of the combinatorial edge

delamination test for PMMA adhesion to silicon substrate.

Contributors and Collaborators

A.J. Crosby, R. Song, M. Chiang, A. Karim,

E.J. Amis (Polymers Division, NIST)

Polymer interfaces play a critical role in numerous

technologies including adhesives, paints and coatings,

and biological systems. Previous research has shown

that polymer interface formation and failure is

dependent upon various material, processing, and

environmental parameters. To explore this large

parameter space efficiently, we have developed a

combinatorial adhesion test based on the contact

and separation of a microlens array. Combinatorial

debonding measurement test method and concurrent

simulations of dynamics of debonding at metalsemiconductor interface due to thermal expansion

mismatch are developed.

Alfred J. Crosby and Alamgir Karim

We have developed a Multilens Contact Adhesion

Test (MCAT) to meet the demands of industry for

a quantitative combinatorial technique to measure the

adhesive strength of polymeric interfaces. Specifically,

the MCAT involves a planar array of spherical caps

(Figure 1(a)) contacting and separating from a

complementary substrate. Using optical tracking of

the contact area at each spherical cap and the measured

relative displacement, we quantify the interfacial strength

on an absolute scale. By fabricating the planar array,

complementary substrate, or both using established

gradient processing techniques, a combinatorial map of

polymer adhesion can be produced. This combination

of the MCAT with gradient library processing facilitates

high-throughput screening of the effect of polymer

adhesion phenomena. Initial demonstration measurements

explored the effect of annealing temperature and coating

thickness on the self-adhesion of thin polystyrene and

Combinatorial Methods
23

High-Throughput Mechanical Properties of Polymer Films

Thin films are increasingly being used in technological

applications involving dielectric coatings, resist layers

for lithography, electronic packaging, optical coatings,

etc. The mechanical properties of these films is

paramount for their effective utilization, but no

high-throughput protocol to measure the mechanical

properties of thin films has been available. We have

developed a novel technique that rapidly measures

the Young’s modulus of thin film coatings from MPa

to GPa. We also extend the copper grid test, a

well-established method for studying crazing and

fracture of glassy polymer films, to measurements

in gradient thin film libraries.

Christopher M. Stafford and Alamgir Karim

As technology continues to move towards smaller,

 thinner, lighter devices, polymeric thin films are

increasingly being used as protective coatings, adhesives,

and functional coatings in such devices. There is a growing

need for test methods that can measure the mechanical

properties (modulus, viscoelasticity, plastic deformation)

of thin films since these material properties play a vital role

in the ultimate performance of the end product. We present

here a reliable, high-throughput technique by which the

elastic modulus of a thin polymer film can be measured.

This technique relies upon a highly periodic strain-induced

buckling instability that arises from a mismatch of the moduli

of a relatively stiff polymer coating on a soft silicone sheet.

The modulus-dependent buckling wavelength, typically

(1 to 10) μm for 100 nm thick glassy films, is rapidly

measured by conventional light scattering. This technique

is ideally suited for measurements of combinatorial libraries

prepared by existing methodologies developed at NIST.

“The authors have come up with a novel way to

quickly measure the elastic modulus of thin film samples.

I am convinced that this technique will quickly find its

way to industrial application and help in the development

of better materials.”

K. Krishana

Sr. Scientist, Rhodia Inc.

The ductile copper grid to support and deform thin

polymer films, developed more than 20 years ago for

uniform films, is extended to study fracture properties of

thin polymer films with gradient properties (i.e., molecular

weight, tacticity, etc.). To validate and demonstrate this

approach, the effects of film thickness, h, on craze structure

was studied by transferring thickness gradients of isotactic

polystyrene prepared by flow coating onto a copper grid

and applying uniaxial strain (Figure 3). The crystallization

morphology and kinetics of isotactic polystyrene (i-PS)

were mapped previously using high-throughput techniques.

Crazes, which lead to fracture in glassy polymers, can

then be correlated to the morphology of crystalline i-PS

on identically prepared gradient libraries to ultimately

obtain structure– (mechanical) property relationship in

a combinatorial manner.

Contributors and Collaborators

C.M. Stafford, C. Harrison, K. Beers, A.J. Crosby,

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

Figure 3: A gradient thickness film of i-PS supported

on a copper grid and mounted on a strain stage (left).

An optical image of post-strain of one square grid showing

craze structures (right).

Figure 1: Setup of combi-thin film modulus apparatus.

As an example, Figure 2 shows the measured modulus

of polystyrene films upon addition of dioctylphthalate

(DOP). The modulus decreases in a sigmoidal fashion

with increased loading of DOP. We are currently extending

this technique to nanocomposite films, UV-curable coatings

and adhesives, and multicomponent formulations.

Figure 2: Modulus of PS films as a function of loading

(mass fraction) with a common plasticizer, dioctylphthalate.

Combinatorial Methods
24

Mapping the Effects of a Nucleating Agent on

Polymer Crystallization

Crystallization rate is an important parameter in industrial

processing of crystalline polymeric materials, affecting

the cost-effectiveness of applications by influencing

factors such as mold dwell times and processing

temperatures. Nucleating agents can be used to control

the rate of crystallization and affect the clarity, fracture

toughness, and overall modulus in the host material.

Using high-throughput methods, we investigate as a

function of film thickness and undercooling temperature

the effectiveness of 4-biphenyl carboxylic acid as a

nucleating agent for polypropylene thin films.

Marlon L. Walker and Alamgir Karim

The advent of new catalytic techniques have

 resulted in the production of a wide variety of new

polypropylenes with different molecular masses, branch

content, and potentially novel chemistries. Use of these

materials in various applications requires comprehensive

evaluation of parameters such as crystallization rate,

which directly affects the cost-effectiveness of the

process. Nucleating agents can influence crystallization

rate and alter the parameters in processing, allowing

for better control of crystallization. A high-throughput

method of evaluating the effects of nucleating agents

on crystallization rate as a function of film thickness

(h) and temperature (T) has been developed based on

the gradient film technology developed in the Polymers

Division at NIST.

Isotactic polypropylene films, neat and with

4-biphenyl carboxylic acid (BCA) as the nucleating

agent, were made using the NIST flow coating

technique. The film samples, having a gradient in h

nominally between 50 nm and 150 nm, were annealed

at 190 oC and then directly placed on a cooling stage

possessing a temperature gradient between 100 oC and

140 oC, orthogonal to the thickness gradient. Optical

images were taken before annealing and at regular

intervals after placement on the gradient stage, allowing

the evaluation of film behavior as a function of thickness

and undercooling temperature with respect to time.

In Figure 1 is a subset of the optical data set taken

using combinatorial methodologies for polypropylene

with BCA. This montage of images represents 16

different (h,T) combinations at virtually the same time.

It can be seen readily that crystallite size and extent

of crystallization increase with higher undercooling

(lower temperatures). Figure 2 is a graph of the radial

growth in time of the three crystallites present at the

point in the optical subset located at a film thickness

of 140 nm ± 2 nm and 125 oC. Crystallite growth can

be followed as a function of time, yielding valuable

information concerning the effectiveness of nucleating

agents in crystallization.

These results help establish a high-throughput

methodology for evaluating the effects of nucleating

agents in polypropylene thin films. Ongoing projects in

the Division indicate that this combinatorial method of

nucleating agent evaluation is applicable to other polymer

materials as well.

Contributors and Collaborators

M.L. Walker, S.A. Buntin (Surface and Microanalysis

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

Division, NIST); A.P. Smith (Columbian Chemical

Company, Marietta, GA)

Figure 1: Subset of high-throughput data set of optical

images of polypropylene containing 4-biphenyl carboxylic acid

undercooled at different temperatures for different thicknesses.

Magnification is 500X.

Figure 2: Crystallite sizes as a function of time at 125 oC

and an initial film thickness of approximately 140 nm.

Combinatorial Methods
25

Interface of Materials with Biology

New materials and devices are radically changing

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 yet 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.

Five major activities constitute this program:

■ The dental industry is primarily composed of small

manufacturers with very little R&D capability. The

dental materials projects, carried out in collaboration

with the American Dental Association, located in the

Polymers Division, fill that gap by developing improved

materials and techniques, patenting and licensing these

inventions, and, most importantly, providing technical

assistance to the licensees for producing and improving

their products. This has provided U.S. companies with

products that successfully compete in a worldwide

market. Our research focuses on improved understanding

of the synergistic interaction of the phases of polymerbased 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.

■ In this era of interdisciplinary approach to research,

the Materials Reliability Division is providing an added

dimension to studying diseases and cellular function. 

By taking a physical/mechanical approach to how

cells function, respond, and remodel, we are able

to provide insight into the progression of diseases

using knowledge and skill sets typically absent in the

biomedical community. We concentrate on mechanical

property metrology for several biological systems,

including natural as well as engineered tissue and

spanning a considerable size range from individual

neurons and muscle cells to complete pulmonary

arteries. This necessitates the development of

unique mechanical testing platforms ranging from

electrical and mechanical probes of individual living

cells to biaxial stressing systems. We interpret our

measurements by focusing on the roles of structural

elements such as cells, composition, and tissue

anisotropy. This classical materials science approach

to understanding properties is proving invaluable to

the biomedical community.

■ 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. Work in the Polymers

Division seeks to bridge the gap between knowledge

generation by cell biologists and product development

in industry. In collaboration with the Chemical Science

and Technology Laboratory, we are developing

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 methods to use

reference substrates that induce specific cellular

responses and engineered DNA vectors that act as

fluorescent reporters of cellular responses.

■ Regenerating form and function to bone defects in

an elderly, osteoporotic population of Americans is

a daunting challenge. To meet this challenge, the

Polymers Division is collaborating with the American

Dental Association to develop metrology methods to

characterize the biocompatibility of synthetic bone

grafts. Quantitative methods being developed include

assays for adhesion, viability, proliferation, and

differentiation of bone cells, as well as optical

coherence tomography and confocal microscopy

for measuring tissue ingrowth. The combinatorial

approach is used to rapidly identify compositions

and surface features 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 self-assembly, 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 much of 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: Eric J. Amis

Program Overview
26

Structure–Property Relationships in Dental Polymers

Polymer based dental materials are increasingly being

used 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.

Joseph M. Antonucci

This project is directed toward building

 fundamental understanding of how monomer

structure, comonomer compositions, and initiator

systems can influence the photopolymerization process

and matrix formation of polymeric dental materials,

e.g., composites. With composites, the influence of both

the filler and interfacial phases also must be considered

as critical factors affecting matrix formation and ultimate

composite properties. Usually, dental matrix polymers

are described simply as highly cross-linked networks

with little or no chemical structural characterization done

beyond a measurement of final vinyl conversion. Although

the results of physical and mechanical property testing

also have been widely reported for dental polymers,

these data are more useful when correlated with the

effects of monomer structural and resin compositional

variations on the development of cross-linked polymers.

A similar but more difficult challenge exists with regard

to finding generalizable structure–property correlations

in composites.

In addition, this project is intended to define the

currently unknown co-reactivity of structurally different

co-monomers than those that are typically used in the

formation of dental polymers. For lack of this type of

information, the reactivity and cross-linking potential of

dental methacrylate monomers are generally assumed

to be equal. The use of selected model monomers is

designed to demonstrate the influence of specific

structural features on monomer reactivity and polymer

properties. Such information should have a significant

impact on the processing and development of improved

materials. An examination of the polymerization of nonmethacrylate vinyl monomers, such as vinyl esters and

vinyl ethers, with conventional dental monomers such as

Bis-GMA offers a means to modify network formation

and ultimately dental polymers/composites. For example,

it was shown that modification of a typical Bis-GMA

dental resin composite with neo-decyl vinyl ester

improved flexural strength when compared to that

of the unmodified composite.

Recently, we employed near infrared (NIR) spectroscopy

in the analysis of dental polymers and demonstrated

its ability to monitor both vinyl conversion and water

absorption. Also with NIR spectroscopy, it is relatively

easy to determine how the filler phase of composites

can influence both vinyl conversion and water uptake of

clinically relevant size composite specimens. In contrast

to conventional gravimetric water sorption studies, NIR

spectroscopy allows the differentiation between free

water and water that is hydrogen-bonded either with

one or with two hydrogen bonds, thereby elucidating

the type of hydrophilicity of the polymer network. NIR

spectroscopy also can be used, more effectively than

mid-IR spectroscopy, to monitor the conversion of

oxirane (epoxy) monomers during and after their

photo-cationic polymerization (Figure 1) as well as the

synthesis of hydroxylated methacrylates from epoxy

monomers such as glycidyl methacrylate.

Figure 1: Siloxane-epoxide / TEGDMA comonomer mixtures.

Currently, we are investigating several high-molecular

mass-alternative resins to Bis-GMA, as well as new

types of high-molecular mass-diluent monomers, for

their efficacy in reducing residual vinyl unsaturation,

polymerization shrinkage, stress and water uptake.

Alternative initiator systems are also under investigation

in an effort to enhance photopolymerization efficiency

and improve the quality of polymer matrix formation.

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 networks as a

means of achieving materials with optimal properties.

Contributors and Collaborators

J.M. Antonucci, M.D. Weir, D.W. Liu, N.D. Richards

(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
27

Figure 3: Sample RT-PCR experiment showing a trial

using 4.4 μm and 1.4 μm poly(methyl methacrylate)

particles and 264.7 macrophages.

Contributors and Collaborators

N. Washburn, F. Wang, L. Bailey, C. Simon,

C. Khatri (Polymers Division, NIST); T. Quinn,

D. McColskey (Materials Reliability Division, NIST);

W. Guthrie (Statistical Engineering Division, NIST);

Industrial and academic collaborators: NIAMS, NIDCR,

FDA, ATS, Rutgers

Once implanted, these devices can elicit serious

inflammatory responses from the patient. The main cells

responsible for these responses are the macrophage,

which coat the device and attempt to consume it.

Macrophage response is mediated through soluble

signaling molecules called cytokines, and we are

adapting real-time polymerase chain reaction (RT-PCR)

techniques to help predict cellular response (Figure 3).

Characterization and Modeling of Tissue Engineering Scaffolds

Polymeric scaffolds form the basis for a wide range

of potential therapies being developed by the tissue

engineering industry. In the Polymers Division, we are

developing a measurement infrastructure to meet the

needs of this growing field by providing reference

materials and test methods for measuring structure,

mechanical properties, rates of cell infiltration and

adhesion, and immune responses.

Newell Washburn and Francis Wang

The tissue engineering industry is faced with a broad

 range of complex measurement issues. The devices

these companies are producing have strict requirements

on mechanical performance, ability to guide tissue

development, and the inflammatory responses provoked

by the implants. We are developing a measurement

infrastructure to meet these needs. Of particular

importance is the development of meaningful in vitro

tests for assessing these parameters. Such tests would

greatly reduce research and development costs where

screening products in animal tests represents a

significant expenditure.

Porous polymeric scaffolds are the basis for

many of the therapies currently under development.

A representative scaffold, produced in our labs, is

shown in Figure 1. The device is made of a

biocompatible polyester and has a continuous

network of pores with characteristic diameter on the

order of 100 μm.

The mechanical performance of the scaffold is

also greatly influenced by the microstructure. The bulk

modulus may be reduced by two orders of magnitude

over that of the solid polymer, which may limit their use

in load-bearing applications. A sample stress-strain

curve is shown in Figure 2 and the nonlinear response

is attributed to failures occurring in different structural

elements. The elements leading to such failures need

to be controlled during device processing, and we are

developing sensitive mechanical tests to be complemented

by three-dimensional structural characterization in order

to prepare guidelines for quality control.

Figure 1: Porous polymer scaffold for tissue engineering

applications.

This porous network is designed to allow cells to

infiltrate and permeate the scaffold to initiate tissue

development. The rate at which this process occurs is

a crucial factor in determining the performance of the

device. We are developing transmigration assays to

measure this using a collagen gel as a model extracellular

matrix. Scaffolds are embedded in a gel and removed

after several days. The rate of cell migration from the

gel to the scaffold is assessed using fluorescence

microscopy and correlated with structural features

of the scaffold surface.

Figure 2: Stress-strain curve for tissue engineering scaffold.

Interface of Materials with Biology
28

Metrology for Tissue Engineering

The tissue engineering industry is developing new

materials and devices that promise to radically change

the medical treatment of injury and disease. In order

to do so, an adequate measurement infrastructure is

necessary to bridge the gap between cell biologists,

materials scientists, product engineers, and regulatory

agencies. To meet this need, we are developing a library

of reference materials, high-throughput techniques for

screening material libraries, and an informatics approach

for data analysis and interpretation.

Scott Kennedy and Newell Washburn

The Polymers Division seeks to extend high throughput

 materials characterization into the realm of biomaterials

and tissue engineering. Considering the vast parameter

space facing the tissue engineering industry, extending

NIST expertise into this arena follows naturally. The effort

has evolved into developing three interwoven toolsets:

material library preparation, high-throughput screening,

and statistical treatment of population distributions.

The library of materials available for investigating

cell-biomaterial interactions continues to expand. At

present, the library encompasses the following material

parameter space: surface energy, crystallinity, roughness,

topological patterns, compliance, degradability, and a

limited range of chemical patterns. Gradient sample

preparation facilitates exploring these discreet

parameters; Figure 1 illustrates the power of the

gradient methodology applied to crystallinity.

underscore the framework established for streamlining

the process of screening cell-material interactions.

■ A fully automated, multi-channel image acquisition

system is operational and capable of z-stack compiling

for auto-focusing or extended depth of field imaging.

■ A versatile image analysis software package with

integrated macros reduces image files to data files.

■ A versatile graphing and analytical software package

with integrated macros performs rigorous statistical

analysis and facilitates data visualization.

At present, image files are reduced to data files

that document general cellular information such as

area, perimeter, roundness, and asymmetry. As more

sophisticated cell-staining protocols are added to the

existing arsenal, data files will include more specific

information describing cell populations.

The power of the streamlined process manifests

itself in that information from thousands of adherent

cells can be documented in a reasonable amount of time.

Thus, screening cell-biomaterial interactions can now

be based on a rigorous statistical comparison of large,

unbiased populations. The significance of this effort

was evident at a recent Gordon Conference where this

work generated interest amongst industrial and academic

representatives alike. Figure 2 illustrates a working

standard by which cell populations could be qualitatively

and quantitatively compared.

Figure 1: AFM images taken across a PLA film annealed

under a temperature gradient (top), and fluorescence

microscopy images of cells fixed and stained 72 hours

after uniform seeding (bottom).

Figure 2: Population distributions from a PCL control

(red) and structurally similar sugar containing polyesters

(black). All distributions were smoothed using a kernel

density estimator and represent a sampling of approximately

1000 cells. Quantitative comparisons result from a two

sample Kolmogorov–Smirnov test against the null hypothesis

This work has attracted interest from potential that both samples come from the same distribution.

customers as the expanding library of gradient materials

may help to identify and develop benchmark SRMs.

Toward this end, strategies are being fleshed out for

preparing orthogonal gradients and decorating surfaces

with functional groups. An automated peptide synthesizer

is also being integrated into this effort.

Initial progress in library preparation exposed

image acquisition and analysis as bottlenecks in the

high-throughput approach. The following highlights

Contributors and Collaborators

S. Kennedy, N. Washburn, L. Bailey, A. Sehgal,

C. Simon (Polymers Division, NIST); A. Plant, J. Elliott

(Biotechnology Division, NIST); W. Guthrie (Statistical

Engineering Division, NIST); Industrial and academic

collaborators: NICHHD, NIDCR, FDA, ATS, ILS,

Rutgers University, Brooklyn Polytech

Interface of Materials with Biology
29

Materials for Micro- and Optoelectronics

U.S. microelectronics and related industries are in

fierce international competition to design and produce

smaller, lighter, faster, more functional, and more reliable

electronics products more quickly and economically

than ever before. At the same time, there has been a

revolution in recent years in new materials used in all

aspects of microelectronics fabrication.

Since 1994, the NIST Materials Science and

Engineering Laboratory (MSEL) has worked closely

with the U.S. semiconductor, component, packaging,

and assembly industries. These 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. The vision that accompanies

this program — to be a key resource within the Federal

Government for materials metrology development for

commercial microelectronics manufacturing — is

targeted 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 micro- and opto-electronics and

magnetic data storage.

With these objectives in mind, the program presently

consists of projects led by the Metallurgy, Polymers,

Materials Reliability, and Ceramics Divisions that examine

and inform industry on key materials-related issues.

These projects are conducted in concert with partners

from industrial consortia, individual companies, academia,

and other government agencies. The program is

strongly coupled with other microelectronics programs

within government and industry, including the National

Semiconductor Metrology Program (NSMP) at NIST.

Materials metrology needs are also identified through

industry groups and roadmaps including the International

Technology Roadmap for Semiconductors (ITRS),

International SEMATECH, the IPC-Embedded Passive

Devices Taskgroup, the IPC Lead-free Solder Roadmap,

the National Electronics Manufacturing Initiative (NEMI)

Roadmap, the Optoelectronics Industry Development

Association (OIDA) roadmaps, and the National

[Magnetic Data] Storage Industry Consortium (NSIC).

Although there is increasing integration within

various branches of microelectronics and optoelectronics,

the field can be considered to consist of three main

areas. The first, microelectronics, includes needs

ranging from integrated circuit fabrication to component

packaging to final assembly. MSEL programs address

materials metrology needs in each of these areas,

including, for example, lithographic polymers and

electrodeposition of interconnects, electrical, mechanical,

and physical property measurement of dielectrics

(interlevel, packaging, and wireless applications), and

packaging and assembly processes (lead-free solders,

solder interconnect design, thermal stress analysis, and

co-fired ceramics).

The second major area is optoelectronics, which

includes work that often crosses over into electronic and

wireless applications. Projects currently address residual

stress measurement in optoelectronic films, and wide

bandgap semiconductors. Cross-laboratory collaborations

with EEEL figure prominently in this work.

The third area is magnetic data storage, where the

market potential is already large and growing and the

technical challenges extreme. NSIC plans to demonstrate

a recording density of 40 times today’s level by 2006.

To reach these goals, new materials are needed that have

smaller grain structures, can be produced as thin films,

and can be deposited uniformly and economically. New

lubricants are needed to prevent wear as the spacing

between the disk and head becomes smaller than the

mean free path of air molecules. MSEL is working with

the magnetic recording industry to develop measurement

tools, modeling software, and magnetic standards to help

achieve these goals. MSEL works in close collaboration

with the Electronics and Electrical Engineering Laboratory,

the Physics Laboratory, the Information Technology

Laboratory, and the Manufacturing Engineering Laboratory

as partners in this effort.

Contact: Eric K. Lin

Program Overview
30

Characterization of Porous Low-k Dielectric Constant Thin Films

NIST is working to provide the semiconductor

industry with unique on-wafer measurements of the

physical and structural properties of porous thin films

important to their use as low-k dielectric materials.

The methodology utilizing several complementary

experimental techniques to measure the average

pore and matrix morphology has been expanded to

include pore size distributions. New methods have

been developed to measure closed pore content and

matrix morphology in films having complex structures

with any morphological type.

Barry J. Bauer and Wen-li Wu

The next generation of integrated circuits will require

 feature sizes that demand new low-k interlayer

dielectric materials. To address problems with power

consumption, signal propagation delays, and crosstalk

between interconnects, dielectric constants will have

to reach unprecedented values. One avenue to low-k

dielectric materials is the introduction of nanometer

scale pores into a solid film to lower its effective

dielectric constant. While these modifications change

the dielectric constant favorably, other important

parameters such as physical strength and barrier

properties will also change, often in an unfavorable

way. Characterization of the pore structure is crucial to

rapid development of new dielectric materials, and new

measurement methods are necessary.

The small sample volume of 1 μm films and the

need to characterize the films on silicon wafers narrows

the number of available measurement methods. We

have been providing standard characterization using a

combination of small angle neutron scattering (SANS),

high-resolution x-ray reflectivity (HRXR), and ion

scattering techniques. These measurements are

performed directly on films supported on silicon

substrates so that processing effects can be investigated.

New methods are required, however, to provide more

detailed information necessary to complete the product

development.

During the past year, we have continued our

efforts on characterization of current industriallyrelevant materials through International SEMATECH,

and by new collaborations with Dow Chemical and IBM.

More significantly, we have perfected new techniques

for more thorough and accurate film characterization.

International SEMATECH, a consortium of

microelectronics companies, provided more than

20 separate samples for characterization by NIST.

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.

Member companies make extensive use of the data to

guide the development of low-k dielectric materials for

integration into future devices.

Finally, we have evaluated and perfected new

measurement methods to more thoroughly and

accurately characterize pore and matrix morphology.

Capillary porosimetry has been applied to HRXR

measurements to determine pore size distributions,

rather than simple averages. By the use of a carrier gas

and control of vapor pressure through thermal methods,

the accuracy and speed of the measurements have

greatly improved. Based on these findings, an automated

measurement system has been designed and is under

construction with the ultimate goal of providing a

measurement technique that can be transferred to the

materials suppliers and chip manufacturers.

Figure 1: Representative mass gain and pore size

distribution calculated from HRXR porosimetry

measurements (AU = arbitrary units).

New techniques have been developed that measure

SANS from films that have been infused by mixtures of

normal toluene and toluene in which hydrogens have

been replaced by deuterium. The match point measures

where the neutron contrast matches that of the wall

material. By filling the open pores with contrast match

fluids, SANS reveals the closed pore content and size.

The relative open and closed pore content is becoming

increasingly important to low-k applications.

Contributors and Collaborators

B.J. Bauer, H.J. Lee, R.C. Hedden, C.L. Soles,

H. Wang, D. Liu, W.L. Wu (Polymers Division, NIST);

C. Glinka (NIST Center for Neutron Research);

J. Wetzel, J. Lee (International SEMATECH);

B. Landes (Dow Chemical); M. Baklanov (IMEC);

D. Gidley (University of Michigan); W. Chen,

E. Moyer (Dow Corning); S. Yang (Lucent)

Materials for Micro- and Optoelectronics
31

Dielectric Metrology for Polymer Composite Films

in the Microwave Range

Novel dielectric hybrid materials based on organic resins

and ferroelectric ceramics with high dielectric constants

have been identified by the industry as key dielectrics

for advancing miniaturization and functional performance

of microwave electronics. The objective of this project is

the development of broadband dielectric metrology for

such materials and fundamental understanding of the

high frequency relaxation mechanism in relation to

structural and molecular attributes.

Jan Obrzut

We have developed an accurate broadband

measurement technique that enables dielectric

measurements at microwave frequencies of up to several

GHz. The broadband test methods currently in use

by the industry are based upon a lumped element

approximation and are limited to frequencies below a

few hundred megahertz. Our new technique is based on

the observation and theoretical analysis of fundamental

mode propagation at high frequencies in thin film

dielectrics terminating a coaxial air-filled transmission

line. The 3D vector plot of the electric field of the first

fundamental mode, simulated inside a high-k specimen,

is shown in Figure 1.

The new broadband methodology enables

measurements at frequencies of 100 MHz to 10 GHz

with the precision required by new electronic technologies.

In partnership with the Institute for Interconnecting and

Packaging Electronic Circuits, IPC, we initiated a standard

test method development and chair the IPC-D37-d test

method subcommittee for Embedded Passive Devices.

We guided the design of the test protocol and made

arrangements with co-sponsoring member companies

for round robin evaluation.

Our capability to measure the dielectric relaxation

times in the sub-nanosecond regime and the relaxation

strength for wide range of dielectric permittivity values

is used to quantify dispersion, alignment, and structure

in hybrid materials. Using the broadband study, we

demonstrated that the composites of organic polymer

resins filled with ferroelectric ceramics exhibit a

dominant intrinsic high-frequency relaxation behavior.

Such dielectric properties were beneficial in eliminating

the electromagnetic noise in processors and logic

devices. We have confirmed that the fastest dielectric

relaxation process is controlled by the dipolar dynamics

of the polymer matrix while the dielectric loss arises

from the difference in coupling between the relaxed

and unrelaxed dipoles. Our new numerical models can

quantitatively correlate the dependence of the real and

imaginary parts of the complex permittivity on the

volume fraction of the ceramic filler.

We have developed constrained regularization

algorithms to obtain a continuous distribution function

of relaxation times. The method is able to resolve

multiple relaxation processes without any a priori

assumptions about their character. It may be generalized

to different types of fundamental relaxation processes

and not restricted to a superposition of Debye-like

functions. This approach will help judge the identity

between microscopic and macroscopic relaxation

behavior of polymer composite systems. It also allows

us to link broadband dielectric spectroscopy with other

techniques such as time domain spectroscopy, photon

correlation spectroscopy and NMR.

Contributors and Collaborators

O. Anopchenko, N. Noda and J. Obrzut (Polymers

Division); B. Rust (Mathematical and Computational

Sciences Division); R.Croswell (Motorola);

R. Charbonneau (Storage Tech.); D. McGregor

(DuPont); T. Hubbing (University of Missouri);

R. Greenlee (Merix); J. Murry (Litton); Tom Newton

(IPC); R. Foly (DOD); J. Peiffer (3M); L. Patch

(NCMS); D. Senk (Shipley); R. Sheffield (Nortel)

Figure 1: The vector plot of the electric field, E,

of the first fundamental mode inside the film specimen

(ε* = 34.6 – j1.6) terminating an AP-7 coaxial line.

The arrows indicate the direction and strength of the

electric field E.

In contrast to the assumption of the lumped element

model, the field in the specimen section is not uniform.

At a resonant frequency of about 8.2 GHz, the magnitude

of the electric field, E, shows two maxima localized near

the edge of the specimen, while the minimum magnitude

of field E extends along the specimen diameter. The

corresponding plot of the magnetic field, H, is parallel to

the propagation direction. Both E and H fields appear to

decay rapidly at the boundary between the high-k dielectric

and air. The results of numerical simulations confirm

our earlier experimental analysis that, at microwave

frequencies, the film specimen becomes a transmission

line with propagation direction along the film diameter

rather than its thickness.

Materials for Micro- and Optoelectronics
32

Polymer Photoresists for Next-Generation Lithography

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 thickness of the imaging layer approach

the 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.

Eric K. Lin

Photolithography is the driving technology used by

 the microelectronics industry to fabricate integrated

circuits with ever decreasing sizes. In this process, a

designed pattern is transferred to the silicon substrate by

altering the solubility of areas of a polymeric photoresist

thin film through an acid catalyzed deprotection reaction

after exposure to radiation through a mask. 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. Material and transport issues arise

when fabricating structures over these length scales.

To date, the materials and processes needed to fabricate

sub-100 nm features have not been selected.

To advance this key fabrication technology, we

work closely with industrial collaborators to develop

and apply high-spatial resolution and chemically specific

measurements to understand changes in material

properties, interfacial behavior, and process kinetics

at nanometer scales and to provide high-quality data

needed in advanced modeling programs.

Over the past year, we have applied and enhanced

unique measurement methods and computer simulation

tools to provide new insight and detail into the complex

physico-chemical processes used in advanced chemicallyamplified photoresists. These methods include x-ray and

neutron reflectivity (XR, NR), small angle neutron and

x-ray scattering (SANS, SAXS), incoherent elastic

neutron scattering (IENS), near-edge x-ray absorption

fine structure (NEXAFS), combinatorial methods, x-ray

standing waves with fluorescence (XSW), nuclear

magnetic resonance (NMR), molecular dynamics (MD)

simulations, and atomic force microscopy (AFM). In

particular, XR and NR studies with specially designed

model materials were used to profile the reaction front

with nanometer resolution (see Highlights), NEXAFS

measurements have been extended to depth profile the

chemical composition of the top 5 nm of a polymer film

surface, SAXS measurements have been performed in

transmission on patterned structures to complement

earlier SANS studies, and AFM techniques have been

adapted to begin study of the mechanical properties of

interfacial polymer layers and structures.

Figure 1: NEXAFS carbon-edge spectra from the bulk and

surface of a model photoresist before (blue /black) and after

exposure and bake (green /red). A delay time of 5 min was

imposed after exposure and before a bake. The reaction is

incomplete only at the surface (peak signature at arrows)

corresponding to surface base (yellow) contamination as

illustrated.

Our experimental and theoretical methods have been

used to understand important technical problems in the

development of next-generation materials. These topics

include: the spatial evolution of the reaction-diffusion

process as a function of temperature and time; the domain

size and distribution of photoacid generator molecules

within a model photoresist polymer matrix; the microscopic

dynamics of photoresist polymers in thin films; the

segregation and distribution of small molecule

contaminants, solvents, and moisture in ultrathin polymer

layers; investigation of the anti-reflective coating-photoresist

interface for material sources of compromised line-profile

control; development contributions to the measured

line-edge roughness; and the structural characterization

of critical dimensions and line-edge roughness in

lithographically-fabricated patterned structures.

Contributors and Collaborators

E.K. Lin, C.L. Soles, J.L. Lenhart, R.L. Jones,

V.M. Prabhu, F.W. Starr, J.F. Douglas, P.M. McGuiggan,

D.L. VanderHart, W.L. Wu (Polymers Division);

D.A. Fischer, S. Sambasivan, J. Woicik (Ceramics

Division); S.K. Satija, C.J. Glinka (NCNR); D.L. Goldfarb,

M. Angelopoulos (IBM T.J. Watson Research Center);

B.M. Trinque, S.D. Burns, C.G. Willson (University of

Texas); R. Puligadda, Y. Wang, D. Guerrero (Brewer

Science)

Materials for Micro- and Optoelectronics
33

Materials Property Measurements

This program responds both to MSEL customer

requests and to the DOC 2005 Strategic Goal of

“providing the information and framework to enable

the economy to operate efficiently and equitably.” For

example, manufacturers and their suppliers need to

agree on how material properties should be measured.

Equally important, engineering design depends on

accurate property data for the materials that are used.

The MSEL Materials Property Measurement

Program works toward solutions to measurement

problems, on scales ranging from the macro to the

nano, in four of the Laboratory’s Divisions (Ceramics,

Materials Reliability, Metallurgy, and Polymers). The

scope of its activities goes from the development and

innovative use of state-of-the-art measurement systems,

to leadership in the development of standardized

test procedures and traceability protocols, to the

development and certification of Standard Reference

Materials (SRMs). A wide range of materials is being

studied, including polymers, ceramics, metals, and

thin films (whose physical and mechanical properties

differ widely from the handbook values for their bulk

properties).

Projects are directed to innovative new measurement

techniques. These include:

■ Measurement of the elastic, electric, magnetic, and

thermal properties of thin films and nanostructures

(Materials Reliability Division);

■ Alternative strength test methods for ceramics,

including cylindrical flexure strength and diametral

compression (Ceramics Division); and

■ Coupling micromechanical test methods with failure

behavior of full-scale polymer composites through the

use of microstructure-based object-oriented finite

element analysis (Polymer Division in collaboration

with the Automotive Composites Consortium).

The MSEL Materials Property Measurement

Program is also contributing to the development of test

method standards through committee leadership roles

in standards development organizations such as ASTM

and ISO. In many cases, industry also depends on

measurements that can be traced to NIST Standard

Reference Materials (SRMs). This program generates

the following SRMs for several quite different types of

measurements.

■ Charpy impact machine verification (Materials

Reliability Division);

■ Hardness standardization of metallic materials

(Metallurgy Division);

■ Hardness standardization and fracture toughness of

ceramic materials (Ceramics Division); and

■ Supporting the Materials Property Measurements

Program is a modeling and simulation effort to connect

microstructure with properties. The Object-Oriented

Finite-Element (OOF) software developed at NIST is

being used widely in diverse communities for material

microstructural design and property analysis at the

microstructural level.

In addition to the activities above, the Materials

Reliability, Metallurgy, Ceramics, and Polymers Divisions

provide assistance to various government agencies on

homeland security and infrastructural issues. Projects

include assessing the performance of structural steels

as part of the NIST World Trade Center Investigation,

advising the Bureau of Reclamation (BOR) on

metallurgical issues involving a refurbishment of Folsom

Dam, advising the Department of the Interior on the

structural integrity of the U.S.S. Arizona Memorial,

advising the U.S. Customs Service on materials

specifications for ceramics, and advising the Architect

of the Capitol on repair procedures for cracks in the

outer skin of the Capitol Dome.

Contact: Gale Holmes

Program Overview
34

Characterization and Modeling of Failure in Fiber Composites

Failure prediction is critical to the use of fiberreinforced composites in many applications. Multifiber composites are being used to conduct

fundamental studies into the nucleation of failure in

fibrous composites. During this research period, we

have prepared our first sets of model 3-D E-glass

fiber arrays. Research on these arrays showed that

matrix cracks induce more damage to the surrounding

matrix resin. Below 50 μm, fiber-fiber interactions,

as quantified by the interfacial shear strength, were

found to depend on the inter-fiber spacing.

Gale A. Holmes and Charles C. Han

During this research year, the first sets of 3-D

 E-glass fiber arrays were prepared and analyzed

(see Figure 1) using sized and un-sized fibers prepared

by our industrial collaborators. 3-D arrays are necessary

to provide failure behavior information about fully

constrained fibers.

Damage in these specimens will also be monitored

by optical coherence tomography (OCT). Images of the

multi-fiber specimens can be found in the “Multi-modal

Imaging Using Optical Coherence Tomography” project

summary.

At a fiber spacing of 11 μm, the breaks in adjacent

fibers are not random. Random fiber breaks between

fibers occurs when the inter-fiber distance is at least

45 μm (see Figure 3).

Figure 1: 3-D Multi-fiber array of sized fibers. The three

out of focus fibers are on a plane approximately 70 μm

below the in-focus fibers.

Analytical results indicate that matrix cracks induce

more damage to the surrounding matrix resin (see

Figure 2), with the intensity of the damage being

dependent on the inter-fiber spacing. Initial finite element

results (not shown) suggest that the most intense

interaction between the shear bands (see 2001 MSEL

Annual Report) emanating from the matrix crack shown

in Figure 2 and adjacent fibers occurs at a distance of

approximately 15 μm.

Figure 2: Pair of sized (a) and un-sized (b) fibers spaced

≈ 2 fiber diameters apart. These representative images

indicate that matrix cracks induce more damage to the

surrounding matrix resin of adjacent fibers.

Figure 3: Effect of inter-fiber spacing on randomness of

fiber breaks. Note intensity of birefringence pattern between

fibers.

The interfacial shear strength exhibited by the

individual fibers (sized and un-sized) in an array was

found to depend, up to ≈ 50 μm, on the inter-fiber

spacing. The interfacial shear strength above this value

was constant (see Figure 4).

Figure 4: Interfacial shear strength vs. inter-fiber

distance.

Two journal papers are being prepared detailing

the results of this research and several supporting

publications have been prepared and submitted. Results

related to the multi-fiber arrays have also been presented

at several conferences (e.g., SAMPE 2002 and

ANTEC 2002).

Contributors and Collaborators

G.A. Holmes, C.K. Moon, W.G. McDonough,

C.C. Han, M. Cicerone, M.Y.M. Chiang, J.P. Dunkers

(Polymers Division, NIST); E. Pohl (OSi Specialties —

Crompton Corporation); Owens Corning

Materials Property Measurements
35

Materials Structure Characterization

Materials science and engineering is the area of

science concerned with understanding relationships

between the composition, structure, and properties of

materials and the application of this knowledge to the

design and fabrication of products with a desired set

of properties. Thus, measurement methods for the

characterization of materials structure are a cornerstone

of this field. MSEL supports a wide array of techniques

and instrumentation for materials measurements.

Facilities include optical and electron microscopy, optical

and electron scattering and diffraction, and major x-ray

facilities at the National Synchrotron Light Source

(NSLS) at Brookhaven Laboratory, and at the Advanced

Photon Source (APS) at Argonne National Laboratory.

Synchrotron radiation sources provide intense beams

of x-rays enabling leading-edge research in a broad

range of scientific disciplines. Materials characterization

using x-rays from synchrotron sources forms a major

part of the Materials Structure Characterization

Program. This includes the development and operation

of experimental stations at the NSLS and at the APS.

At the NSLS, NIST operates a soft x-ray station

in partnership with Dow and Brookhaven National

Laboratory. At the APS, NIST is a partner with the

University of Illinois at Urbana /Champaign, Oak Ridge

National Laboratory, and UOP, in a collaboration

called UNICAT. At both facilities, NIST scientists, and

researchers from industry, universities, and government

laboratories, perform state-of-the-art measurements on

a wide range of advanced materials. Studies currently

underway include: ceramic coatings; defect structures

arising during deformation of metals, ceramics, and

polymers; defect structures in semiconductors and

single-crystal proteins; and atomic-scale and molecularscale structures at surfaces and interfaces in polymeric,

catalytic, and metal/semiconductor systems.

Ceramic powders are precursors for over 80% of

ceramic manufacturing. As a result, a major focus in

the Ceramics Division is the accurate and reliable

measurement of the physical and chemical properties

of ceramic powders, including sub-micrometer and

nanometer sized powders. These measurements are

critical to ensuring processes and products of high

quality, minimal defects, and consequent economic

benefits. Another area of concern to ceramic

manufacturing is powder dispersion in a fluid vehicle

for shape forming and other uses. The chemical and

physical characteristics of powders dispersed in liquids

are evaluated to understand the influence of surface

charge, dissolution, precipitation, adsorption, and other

physicochemical processes on the dispersion behavior.

In addition to these activities, standard reference

materials for use as primary calibration standards and

national/international standards for particle size and

size distribution, pore volume, and particle dispersion

measurements are being developed in collaboration with

industrial partners, measurement laboratories, and

academic institutions in the U.S., Europe, and Asia.

The NIST effort in materials characterization has

a strong emphasis on electron microscopy, which is

capable of revealing microstructures within modern

nanoscale materials and atomic-resolution imaging and

compositional mapping of complex crystal phases with

novel electronic properties. The MSEL microscopy

facility consists of two high-resolution transmission

electron microscopes (TEM) and a high-resolution,

field-emission scanning electron microscope (FE-SEM)

capable of resolving features down to 1.5 nm. Novel

experimental techniques using these instruments have

been developed to study multilayer and nanometer-scale

materials.

Through this MSEL Program, measurement

methods, data, and standard reference materials

(SRMs) needed by the U.S. polymers industry, research

laboratories, and other federal agencies are provided to

characterize the rheological and mechanical properties

of polymers and to improve polymer processibility.

In response to critical industry needs for in-situ

measurement methodologies, a substantial effort is

underway to develop optical, dielectric, and ultrasonic

probes for characterizing polymer processing. Improved

methods for determining molecular mass distribution

of polymers are developed because of 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,

techniques are being developed that measure the solidstate structure and rheological behavior of polymeric

materials. Recent program activities exploit advances

in mass spectrometry using matrix assisted laser

desorption ionization (MALDI) to develop a primary

tool for the determination of the molecular masses

of synthetic polymers, with particular emphasis on

commercially important polyolefins. The polymer

industry and standards organizations assist in the

identification of current needs for SRMs, and based on

these needs, research on characterization methods and

measurements is conducted leading to the certification

of SRMs.

Contact: Chad R. Snyder

Program Overview
36

Polymer Standards

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 improvement. Research supports

development of standard test methods for

characterizing the molecular structure and use

properties of polymers that are needed to optimize

synthesis of polymers and improve their performance.

Bruno Fanconi and Charles Guttman

NIST supplies the only polyethylene molecular

 mass standards for calibration of size exclusion

chromatographs, the principal instrument used

by industry to characterize the molecular mass

distribution of polymers. This year, we will certify

a replacement for SRM 1483, a polyethylene mass

standard whose supply will soon be exhausted.

Research is conducted in mass spectrometry of

synthetic polymers to provide industry with better

methods to measure molecular mass distribution.

Previous work on polystyrene resulted in the first

polymer molecular mass standard produced with

the complete mass spectrum, measured by mass

spectrometry, as ancillary data. Based on the success

of that work, a collaborative effort was initiated among

standards laboratories in Europe, the U.S. and Japan

to establish a standard protocol for measurement

of the mass distribution of polystyrene by mass

spectrometry. The draft standard method is under

final review by the participating organizations.

Arrangements have been made to submit the method

to standards developing organizations for acceptance

as a standard method.

Three SRMs were produced in the past year that

assist polymer producers and processors in making

reliable measurements of the rheological properties

of polymers. Two of the SRMs are melt flow rate

standards that are employed to calibrate instruments

used to assess the processibility of polymer resins.

The NIST melt flow rate standards are referenced

in the ASTM standard test method that is widely

used to characterize the processibility of polymers.

The third SRM, a poly(dimethylsiloxane) fluid,

is intended primarily for use in calibration and

performance evaluation of instruments used to

determine the 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.

This SRM also serves the needs of instrument

manufacturers and testing laboratories as a

secondary standard for calibrating viscometers.

In recognition of the increasing role of synthetic

polymers in medical applications, we supply reference

materials for test method development, benchmarking

properties, and materials improvement. In response to

recommendations of a NIST/Industry workshop on

reference materials and data needs for medical use of

polymers, an activity was initiated to measure material

properties of acrylic polymers used in intraocular lenses

for generation of reference database and reference

materials. In collaboration with vendors of intraocular

lens (IOL) materials, testing laboratories, the National

Institutes of Health, and LSU Medical school, data

acquisition has commenced on a series of IOL polymers

for the purpose of building a reference material database

and supply of reference IOL biomaterials to aid research

and development of improved materials.

Members of an ASTM subcommittee developing

an improved test method for determination of degree

of crosslinking resulting from irradiation of ultra-high

molecular weight polyethylene, UHMWPE, sought

our assistance in providing NIST RM 8456, a medical

grade UHMWPE, in a form suitable for the method.

Sufficient quantity has been manufactured for issuance

as a reference material for comparisons among different

test methods.

Contributors and Collaborators

W. Blair, B. Fanconi, K. Flynn, C. Guttman,

C. Schultheisz, J. Tesk (Polymers Division, NIST);

S. Leigh (Statistical Engineering Division, NIST)

Materials Structure Characterization
37

Polyolefin Mass Spectrometry

The mass distribution of a polymer is critical to how

they are processed and their resultant properties.

Mass spectrometry, MS, is exploited to characterize

molecular architecture of saturated hydrocarbon

polymers that is difficult, or impossible, to measure

by other methods. The work focused on polyolefins,

the dominant type of commercial polymer, that exhibit

a plethora of molecular architectures owing to

advances in synthesis.

William E. Wallace

Polyethylene and polypropylene dominate the synthetic

 polymer commercial market. Their dominance has

been spurred on by new developments in metallocene

catalysts that provide an unprecedented level of synthetic

control. A polymer’s molecular mass and molecular-mass

distribution are critical in determining its performance

properties. Mass spectrometry is currently the most

promising method for obtaining accurate molecular mass

and absolute molecular mass distributions.

Molecular mass determination by mass spectrometry

requires the formation of intact macromolecular ions

in the gas phase. This is typically accomplished by the

gas-phase association of metal cations (Na+, K+, Cu+,

Ag+) with polar or polarizable functional groups on the

polymer. Polymers that lack such functional groups (like

polyethylene and polypropylene) have not been amenable

to mass spectrometric characterization and cannot be

analyzed for molecular mass distribution using existing

techniques of metal cationization.

In the previous year a new method was introduced

for the mass spectrometry of saturated polyolefins

whereby an organic cation is covalently bonded to

the vinyl end-group of the polymer to produce the

necessary ionization for the creation of intact gas-phase

macromolecules by matrix-assisted laser desorption

ionization (MALDI). This year the “covalent cationization”

methodology was further optimized to produce mass

spectra for higher molecular mass materials than had

been achieved previously by our group and more than

six times greater than found in the literature. (See

Technical Highlight in this report for more details).

The Polymers Division has also researched

the use of organometallic cationization as a way to

create intact gas-phase macromolecular ions of fully

saturated materials. Our goal in the past year was to

develop the methodology for ionization of saturated

hydrocarbon inside the mass spectrometer with minimal

fragmentation. We selected the η5-cyclopentadienyl

cobalt ion (CpCo·+) because, unlike the reactive bare

transition metal ions, it has been shown to react with

short-chain linear alkanes (2 < n < 6) exclusively by

dehydrogenation with no evidence of C-C bond cleavage.

To test the feasibility of the CpCo·+ ion as a

charging agent, we conducted reactivity studies

with three medium chain length n-alkanes using

Fourier-transform ion cyclotron resonance mass

spectrometry. We report that the CpCo·+ ion reacts

predominantly by double dehydrogenation of all three

alkanes with no C-C bond cleavage observed.

The figure below compares mass spectra for

ionization of n-octacosane (C-28) by the existing

bare transition metal cation method (laser desorption

time-of-flight mass spectrometry, LDI-TOF MS)

and our method using the organometallic chemistry

method (Fourier transform mass spectrometry, FTMS).

The reaction of C-28 with Co+ produces the charged

hydrocarbon (adduct) as well as extensive fragmentation.

In contrast, the CpCo·+ ion reaction with C-28 yields

the charged hydrocarbon with minimal fragmentation.

Our goal for FY03 is to extend the organometallic

cationization measurements to low-mass polyolefins.

Contributors and Collaborators

B.J. Bauer, W.R. Blair, H.C.M. Byrd, B.M. Fanconi,

C.M. Guttman, S. Lin–Gibson, D.L. Vanderhart,

W.E. Wallace, A. Weaver, S.J. Wetzel (Polymers Division);

A.J. Kearsley (Mathematical and Computational Sciences

Division); D.A. Fischer (Ceramics Division); L. Li

(University of Alberta); D.R. Ridge (University of

Delaware); J.E. Girard (American University)

Figure 1: Mass spectra ionization using bare transition

metal cation method vs. organometallic chemistry method.

Materials Structure Characterization
38

Multi-Modal Imaging Using Optical Coherence Tomography

The impact of multi-modal imaging is shown most

clearly in medical imaging. By combining magnetic

resonance imaging and positron emission tomography,

the physician diagnoses more effectively than using

either technique alone. This same approach is taken

in our program on multi-modal imaging of materials.

The goal of this work is to gain new insight into material

systems by simultaneously imaging structure, function,

and dynamics. Multi-modal imaging is anticipated to

have the earliest and most direct impact on Division

efforts in tissue engineering and composite mechanics.

Joy Dunkers and Marcus Cicerone

The multi-modal imaging effort is built around a

 technique called optical coherence tomography

(OCT). In short, OCT is a non-invasive, non-contact,

highly-sensitive structural technique for three-dimensional

imaging of highly scattering materials using interferometry.

Our first generation OCT performed structural imaging

only with an axial (z) resolution of 20 μm. This past

year has been spent implementing the second generation

OCT (Figure 1) which not only possesses two types

of functional imaging but also boasts vast improvements

in imaging speed, resolution, and instrument stability.

We have increased the data acquisition speed by 50X

and the modulator accuracy by 6X by implementing a

piezoelectric based fiber modulator.

sensitivity inherent in an optical coherence measurement

and uses a confocal optical configuration to significantly

improve the axial resolution over standard OCT. We obtain

lateral and axial resolutions of 0.5 μm and 1.0 μm.

Confocal fluorescence microscopy has proven to

be a powerful technique for understanding structure–

function relationships, especially in the biological fields.

The C-FL consists of an air-cooled argon ion laser,

optical filters for excitation and emission wavelength

selection, and a photo-multiplier tube detector (Figure 1).

In our instrument, fluorescence is collected from a spot

within the sample that coincides with the near infrared

focal spot. The two types of information are obtained

simultaneously. If the sample contains fluorescent

markers that signify particular function, this technique

yields functional information that is in registration with

the structural information from C-OCT.

PS-OCT allows us to obtain a quantitative, spatially

resolved map of birefringence. Because local structural

strain or macromolecular orientation can lead to optical

birefringence, we can quantify these properties. Circularly

polarized light is used in the sample arm to make the

results independent of sample orientation. Detection of

birefringence is accomplished by monitoring the vertical

(s) and horizontal (p) components of the light returning

from the sample.

PS-OCT images (230 μm wide and 500 μm high)

from a glass fiber and epoxy dogbone (Figure 2) show

intact fibers. Birefringence, and therefore residual stress,

would manifest itself as an extinction of either polarization.

These images show that virtually no residual stress

exists with this large fiber spacing, as expected.

Contributors and Collaborators

G.A. Holmes, W.G. McDonough, N.R. Washburn

(Polymers Division, NIST); J. Bush, S. Bell (Optiphase

Inc., Van Nuys, CA)

J. Dunkers, “Applications of Optical Coherence

Tomography to the Study of Polymer Matrix

Composites,” The Handbook of Optical Coherence

Tomography, B. Bouma and G. Tearney, eds., Marcel

Dekkar, Inc., NY, 2002.

Figure 1: Second generation optical coherence

tomography (OCT).

Three hybrid techniques were developed: confocal

OCT (C-OCT), confocal fluorescence and C-OCT

(C-FL/C-OCT), and polarization sensitive OCT

(PS-OCT). C-OCT takes advantage of the exceptional

Figure 2: PS-OCT images from a glass fiber and epoxy

dogbone at 230 μm wide and 500 μm high show intact

fibers (arrow A).

Materials Structure Characterization
39

Quantifying Dispersion and Properties of

Carbon Nanotube Composites

Small-angle neutron scattering is also being used

to quantify dispersion in composites of polymers and

single-walled carbon nanotubes (SWNT’s). This work

is being done in collaboration with the University of

Pennsylvania. Composite samples prepared at varying

degrees of dispersion have been investigated using

small-angle neurton scattering (SANS), and the shape

of the scattering curve as a function of scattered wave

vector has been used to extract a quantitative measure

of the SWNT dispersion and diameter. Transmission

electron microscopy (TEM) has been used to confirm

the extent of dispersion. In the near future, we will

measure the dielectric spectrum of these polymer

nano-composites and evaluate in-line dielectric

spectroscopy as a tool for quantifying nanotube

dispersion in situ during processing.

Figure 1: Optical data for a PB/MWNT dispersion

(3.5 x 10–3 mass fraction MWNT, T = 40 oC) at a shear

rate of 50.0 s–1. Orientation of the tubes along the vorticity

direction is evident in the micrograph, in the anisotropy of

the hh and vv patterns, and, to a lesser extent, in the

orientation of the intensity lobes in the hv and vh patterns.

The flow direction is horizontal and the vorticity direction is

vertical. The micrograph is 200 μm wide.

Contributors and Collaborators

H. Wang, J. Obrzut, D.L. VanderHart, S.D. Hudson,

H. Kim, S. Lin–Gibson (Polymers Division, NIST);

T. Kashiwagi (Fire Research Division, NIST); E.A. Grulke

(University of Kentucky); K.I. Winey (University of

Pennsylvania); K. McElrath, D. Colbert (CNI)

Materials Structure Characterization

Inorganic fillers are frequently used to enhance

polymer properties. New attributes may be achieved

with exotic nanoparticles, provided that the underlying

science is well developed. Both multi- and single-wall

carbon nanotubes offer the promise of novel polymer

nanocomposites, with potential applications in conducting

plastics, reinforced plastics, flame retarding plastics, and

novel optical materials. Issues of critical importance are

dispersion and alignment, and how these influence bulk

physical properties.

Erik K. Hobbie, Jack F. Douglas,

and Charles C. Han

Nanocomposite materials engineered from polymers

 and carbon nanotubes offer the promise of polymer

composites with greatly enhanced electrical, thermal,

optical, and structural properties. For example,

measurements performed at NIST have recently

demonstrated significantly-enhanced flame retardation

in polypropylene and multi-walled carbon nanotube

composites at loadings of only 1% nanotubes by mass.

As inorganic filler in a polymer matrix, the anisotropy

of carbon nanotubes makes them structurally unique

in that the tube diameter can be the same order of

magnitude as the radius of gyration of the polymer, yet

the aspect ratio of the tubes can be exceptionally large

and the tubes themselves can exhibit extreme mechanical

strength. In addition to the resolution of fundamental

issues concerning the fractionation, functionalization,

and dispersion of multi- and single-walled carbon

nanotubes in a wide array of organic solvents and

polymer matrices, efficient bulk processing of nanotubepolymer composites will depend on both a detailed

understanding of the response of polymer-nanotube

melts to simple steady shear flow and a convenient

but quantitative measure of tube dispersion.

Investigations involving multi-walled carbon

nanotubes (MWNT’s) have focused on developing

an optical metrology for in situ observations of

MWNT’s dispersed in polymer melts under simple

shear flow. These measurements employ polarized

light scattering and optical microscopy to quantify

the structural anisotropy of sheared nanotube melts,

as shown in Figure 1. The requirement is that the melt

be sufficiently dilute or the sample sufficiently thin for

optical measurements to be used. We have mapped out

the orientation of the tubes as a function of Deborah

number in the suspending medium and observed

orientation of the tubes along both the flow direction

and the vorticity direction. We anticipate that these

measurements will have applications in the injection

molding of conducting plastic parts, for example.
40

Characterization and Modeling of the Interfaces and

Interphases of Polyolefin Blends

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 rheological,

morphological, and interfacial properties of multiphase

polymer blends as a function of processing parameters,

such as composition, shear stress, and crystalline

structure. Constitutive relationships are formulated

for process modeling needs.

Charles C. Han, Howard Wang,

and Frederick R. Phelan, Jr.

During the past year, extensive experimental work

 has been carried out to understand the effect of

blending and thermal history on structure development

in polyethylene-hexene/polyethylene-butene (PEH/PEB)

blends employing both real and reciprocal space techniques.

This work represents the first comprehensive investigation

of polymer blends that exhibit both liquid phase separation

and crystallization.

Using phase-contrast optical microscopy, both

crystal super-structure growth and phase-separation

kinetics were measured in blends of various compositions

at various temperatures. Measurements of crystal-growth

kinetics show that blends and pure PEH exhibit similar

growth regimes. Phase-separation in the blends is very

slow, and nonlinear hydrodynamic effects dominate the

domain coarsening. Atomic force microscopy studies

show that the surface crystal morphology can be

fibrous, spherulitic, or dendritic depending on both

composition and quench depth. Transmission electron

microscopy reveals bulk semi-crystalline morphology

in more detail. For example, blending with PEB swells

the inter-lamellae spacing, implying the inclusion of

non-crystallizable chains within the lamellar stacks.

In another example, when a critical blend is allowed to

phase separate for an extended period before further

lowering the temperature for crystallization, distinct

lamellar crystals form within the co-existing PEH-rich

and PEB-rich domains, leading to a morphology

characterized by hierarchical length scales.

Simultaneous small and wide-angle x-ray scattering

measurements on crystal growth have been carried

out at the National Synchrotron Light Source (NSLS)

at Brookhaven National Labs (BNL). Isothermal

crystallization of blends, which follow either a 1-step

quench from a homogeneous melt or a 2-step quench

to an intermediate temperature for phase separation

followed by a quench to a lower temperature, has

been studied extensively.

The effect of simple shear flow on crystallites in

suspension in polyolefin blends has been investigated

using light scattering and microscopy. To account for

both the structural anisotropy and the flow-induced

orientation, polarized light scattering is employed, with

the polarizer and analyzer set at horizontal (H) and

vertical (V) orientations (parallel or perpendicular to the

flow direction, respectively). It is found that crystallites

orient along the vorticity direction at low shear rate,

whereas at high shear rate, crystal super-structures

melt, and the morphology becomes a mixture of large

crystallites oriented along the vorticity direction and

thin lamellae sheets aligned with the flow direction.

After cessation of shear, the crystals aggregate to

form necklace structures and hundred-micron

sized balls.

Simulations of isolated droplets at super-critical

capillary numbers in steady, homogeneous shear flow

have also been carried out using a Lattice Boltzmann

scheme. The goal is to understand drop breakup

mechanisms and develop models for this that can be

applied to complex flows, such as injection molding.

It has been observed that a super-critical droplet first

deforms into an elongated liquid thread with “dumbbell”

type ends. Sub-critical “child” drops pinch off the ends

of the thread in a continual process until the depleted

original is itself below critical. Results for Cao = 0.45

(where Cac = 0.4) are shown in Figure 1, where the

final configuration of the new droplet family is observed.

There are four drops, all stable, below the critical

Capillary number. There is evidence of a distribution in

sizes. The initial child drops that are formed are larger

than subsequent ones.

Figure 1: The final state for case 1. There are four drops

all below critical. The initial “child” drops that are formed

are larger than the subsequent ones.

Contributors and Collaborators

K. Shimizu, G.Z.G. Wang, G. Matsuba, F. Landis,

H. Kim, E.K. Hobbie (Polymers Division, NIST);

N. Martys (BFRL, NIST); B.S. Hsiao (SUNY);

D. Lohse (Exxon)

Materials Structure Characterization
41

Polymers Division FY02 Annual Report Publication List

Characterization and Measurement —

Method Development

Computational Methods

Y. Gebremichael, T.B. Schroder, F.W. Starr, and

S.C. Glotzer, “Spatially Correlated Dynamics in a

Simulated Glass-Forming Polymer Melt: Analysis

of Clustering Phenomena.” Physical Review E 64,

1503–1515 (2001).

N. Giovambattista, F.W. Starr, F. Sciortino,

S.V. Buldyrev, and H.E. Stanley, “Transitions between

Inherent Structures in Water.” Physical Review E 65,

1502 (2002).

S.C. Glotzer, Y. Gebremichael, N. Lacevic,

T.B. Schroder, and F.W. Starr, “Glass-Forming Liquids

and Polymers: With a Little Help From Computational

Statistical Physics.” Computer Physics Communications

146, 24–29 (2002).

H.E. Stanley, S.V. Buldyrev, N. Giovambattista,

E. La Nave, A. Scala, F. Sciortino, and F.W. Starr,

“Statistical Physics and Liquid Water: ‘What Matters’.”

Physica A 306, 230–242 (2002).

F.W. Starr, N. Lacevic, T.B. Schroeder, V.N. Novikov,

and S.C. Glotzer, “Growing Correlation Length of a

Simulated Glass-Forming Liquid.” Physical Review E,

(in press).

F.W. Starr, S. Sastry, E. La Nave, A. Scala,

H.E. Stanley, and F. Sciortino, “Thermodynamic and

Structural Aspects of the Potential Energy Surface

of Simulated Water.” Physical Review E 63,

1201–1210 (2001).

Optical Coherence Tomography

J.P. Dunkers, “Applications of Optical Coherence

Tomography to the Study of Polymer Matrix Composites.”

Handbook of Optical Coherence Tomography,

pp. 421–443, B.E. Bouma and G.J. Tearney, eds.,

(Marcel Dekker, Inc., New York, NY 2002).

J.P. Dunkers, F.R. Phelan, C.G. Zimba, K.M. Flynn,

D.P. Sanders, R.C. Peterson, and R.S. Parnas,

“The Prediction of Permeability for an Epoxy/E-Glass

Composite Using Optical Coherence Tomographic Images.”

Polymer Composites 22, 803–814 (2001).

W.G. McDonough, G.A. Holmes, and J.P. Dunkers,

“An Analysis of the Fiber-Fiber Interactions Using the

Fragmentation Test and Optical Coherence Tomography.”

Proceedings of the Society of Plastics Engineers Annual

Technical Conference, San Francisco, CA, May 2002.

Sum Frequency Generation Spectroscopy

K.A. Briggman, J.C. Stephenson, W.E. Wallace,

and L.J. Richter, “Absolute Molecular Orientational

Distribution of the Polystyrene Surface.” Journal of

Physical Chemistry B 105, 2785–2791 (2001).

L.J. Richter, P.T. Wilson, W.E. Wallace,

K.A. Briggman, and J.C. Stephenson, “Correlation of

Molecular Orientation with Adhesion at Polystyrene/

Solid Interfaces.” Chemical Physics Letters, (in press).

P.T. Wilson, K.A. Briggman, J.C. Stephenson,

W.E. Wallace, and L.J. Richter, “Molecular Order at

Polymer Interfaces Measured by Broad-Bandwidth

Vibrationally-Resolved Sum-Frequency Generation

Spectroscopy.” Quantum Electronics and Laser Science

Conference, 2001 Technical Digest, 2002.

P.T. Wilson, K.A. Briggman, W.E. Wallace,

J.C. Stephenson, and L.J. Richter, “Selective Study of

Polymer/Dielectric Interfaces with Vibrationally Resonant

Sum Frequency Generation via Thin Film Interference.”

Applied Physics Letters 80, 3084–3086 (2002).

Characterization and Measurement —

Standards & Data

Mass Spectrometry

B.J. Bauer, H.C. Byrd, and C.M. Guttman, “Small

Angle Neutron Scattering Measurements of Synthetic

Polymer Dispersion in Matrix-Assisted Laser Desorption

Ionization Matrixes.” Rapid Communications in Mass

Spectrometry 16, 1494–1500 (2002).

B.J. Bauer, C.M. Guttman, D.W. Liu, and

W.R. Blair, “Tri-±-naphthylbenzene as a Crystalline or

Glassy Matrix for Matrix-Assisted Laser Desorption /

Ionization: A Model System for the Study of Effects of

Dispersion of Polymer Samples at a Molecular Level.”

Rapid Communications in Mass Spectrometry 16,

1192–1198 (2002).

B.J. Bauer, S. Lin–Gibson, L. Brunner,

D.L. VanderHart, B.M. Fanconi, C.M. Guttman,

and W.E. Wallace, “Optimization of the Covalent

Cationization for the Mass Spectrometry of Polyolefins.”

Proceedings of the 50th American Society of Mass

Spectrometry Conference on Mass Spectrometry and

Allied Topics, 50, Orlando, FL, June 2002.

B.J. Bauer, W.E. Wallace, B.M. Fanconi, and

C.M. Guttman, “ ‘Covalent Cationization Method’ for

the Analysis of Polyethylene by Mass Spectrometry.”

Polymer 42, 9949–9953 (2001).

Polymers Division FY02 Annual Report Publication List
42

H.C.M. Byrd, C.M. Guttman, and D.P. Ridge,

“Chemical Ionization of Saturated Hydrocarbons Using

Organometallic Ion Chemistry.” Proceedings of the 50th

American Society of Mass Spectrometry Conference

on Mass Spectrometry and Allied Topics, Orlando, FL,

June 2002.

R. Chen, T. Yalcin, W.E. Wallace, C.M. Guttman,

and L. Li, “Laser Desorption Ionization and MALDI

Time-of-Flight Mass Spectrometry for Low Molecular

Mass Polyethylene Analysis.” Journal of the American

Society for Mass Spectrometry 12, 1186–1192

(2001).

R. Chen, T. Yalcin, W.E. Wallace, C.M. Guttman,

and L. Li, “Laser Desorption Ionization and MALDI

Time-of-Flight Mass Spectrometry for Low Molecular

Mass Polyethylene Analysis.” Proceedings of the 49th

ASMS Conference on Mass Spectrometry and Allied

Topics, Chicago, IL, May 2001.

C.M. Guttman, “Mass Spectrometry.” Encyclopedia

of Polymer Science and Technology, (in press).

S. Lin–Gibson, L. Brunner, D.L. VanderHart,

B.J. Bauer, B.M. Fanconi, C.M. Guttman, and

W.E. Wallace, “MALDI MS Characterization of

Covalent Cationized Polyethylene.” ACS Polymer

Preprints, (in press).

S. Lin–Gibson, L. Brunner, D.L. Vanderhart,

B.J. Bauer, B.M. Fanconi, C.M. Guttman, and

W.E. Wallace, “Optimizing the Covalent Cationization

Method for the Mass Spectrometry of Polyolefins.”

Macromolecules, (in press).

R.E. Tecklenburg, H.P. Chen, and W.E. Wallace,

“Electrospray FTMS and MALDI TOF MS

Characterization of [(O3/2SiMe)x(OSi(OH)Me)y

(OSiMe2)z] Silsesquioxane Resin.” Proceedings of the

49th ASMS Conference on Mass Spectrometry and

Allied Topics, 2001.

R.E. Tecklenburg, W.E. Wallace, and H.P. Chen,

“Characterization of a [(O3/2SiMe)x(OSi(OH)Me)y

(OSiMe2)z] Silsesquioxane Copolymer Resin by

Mass Spectrometry.” Rapid Communications in Mass

Spectrometry 15, 2176–2185 (2001).

W.E. Wallace and C.M. Guttman, “Data Analysis

Methods for Synthetic Polymer Mass Spectrometry:

Autocorrelation.” Journal of Research of the National

Institute of Standards and Technology 107, 1–17

(2002).

W.E. Wallace, C.M. Guttman, B.M. Fanconi, and

B.J. Bauer, “MALDI MS of Saturated Hydrocarbon

Polymers: Polyethylene and other Polyolefins.”

Proceedings of the 49th ASMS Conference on

Mass Spectrometry and Allied Topics, Chicago, IL,

May 2001.

W.E. Wallace, C.M. Guttman, A.J. Kearsley, and

J. Bernal, “Advanced Numerical Methods for Polymer

Mass Spectral Data Analysis.” Proceedings of

the 50th American Society of Mass Spectrometry

Conference on Mass Spectrometry and Allied Topics,

50, Orlando, FL, June 2002.

A.P. Weaver, C.M. Guttman, and J.E. Girard,

“Quantitation of Polymer End Groups Using MALDI

TOF MS.” Proceedings of the 50th American Society of

Mass Spectrometry Conference on Mass Spectrometry

and Allied Topics, Orlando, FL, June 2002.

T. Yalcin, W.E. Wallace, C.M. Guttman, and L. Li,

“Metal Powder Substrate-Assisted Laser Desorption

Ionization Mass Spectrometry for Polyethylene

Analysis.” Proceedings of the 50th American Society of

Mass Spectrometry Conference on Mass Spectrometry

and Allied Topics, 50, Orlando, FL, June 2002.

T. Yalcin, W.E. Wallace, C.M. Guttman, and L. Li,

“Metal Powder Substrate Assisted Laser Desorption

Mass Spectrometry for Polyethylene Analysis.”

Analytical Chemistry, (in press).

Standards

D. Hall and J.A. Tesk, “Workshop on Standards for

Biomedical Materials and Devices.” NISTIR 6791

(2001).

J.R. Maurey, C.R. Schultheisz, W.R. Blair, and

C.M. Guttman, “Certification of Standard Reference

Material 1473b, A Polyethylene Resin.” NIST Special

Publication 260, 144 (2002).

C.R. Schultheisz, K.M. Flynn, and S.D. Leigh,

“Certification of the Rheological Fluid Behavior of SRM

2491, Polydimthylsiloxane.” NIST Special Publication,

147 (2002).

C.R. Schultheisz and G.B. McKenna, “Nonlinear

Viscoelastic Analysis of the Torque, Axial Normal

Force and Volume Change Measured Simultaneously

in the National Institute of Standards and Technology

Torsional Dilatometer.” Journal of Rheology 46,

901–925 (2002).

C.R. Schultheisz and G.B. McKenna, “Standard

Reference Materials: Non-Newtonian Fluids for

Rheological Measurements.” Proceedings of the Society

of Plastics Engineers Annual Technical Conference,

San Francisco, CA, May 2002.

J.A. Tesk, “Reference Materials for Tissue

Engineered Medical Products.” Tissue Engineering,

(in press).

Polymers Division FY02 Annual Report Publication List
43

Characterization and Measurement —

Internal Capabilities

Polymer Crystallization

J.F. Douglas, V. Ferreiro, J. Warren, and A. Karim,

“Observation of Growth Pulsations in Polymer

Dendritic Crystallization in Thin PEO/PMMA Films.”

ACS Polymer Preprints, (in press).

M.J. Fasolka, L.S. Goldner, A.M. Urbas, J. Hwang,

K.L. Beers, P. DeRege, and E.L. Thomas, “Near-Field

Optical Imaging of Microphase Separated and

Semi-Crystalline Polymer Systems.” Microscopy

and Microanalysis, art #291, Quebec City, Canada,

August 4, 2002–August 8, 2002.

V. Ferreiro, J.F. Douglas, J. Warren, and A. Karim,

“Non-Equilibrium Pattern Formation in the Crystallization

of Polymer Blend Films.” Physical Review E, (in press).

V. Ferreiro, J.F. Douglas, J.A. Warren, and A. Karim,

“Growth Pulsations in Symmetric Dendritic Crystallization

in Thin Polymer Films.” Physical Review E, (in press).

P. Kofinas, P.L. Drzal, and J.D. Barnes,

“Path Dependent Microstructure Orientation During

Plane Strain Compression of Semicrystalline Block

Copolymers.” Polymer 42, 5633–5642 (2001).

Gelation, Diffusion and the Glass Transition

D. Bedrov, G.D. Smith, and J.F. Douglas,

“Influence of Self-Assembly on Dynamical and

Viscoeleastic Properties of Telechelic Polymer

Solutions.” Europhysics Letters, (in press).

D. Behar, P. Neta, and C.R. Schultheisz,

“Reaction Kinetics in Ionic Liquids as Studied by

Pulse Radiolysis: Redox Reactions in the Solvents

Methyltributylammonium Bis(trifluoromethylsulfonyl)imide and N-Butylpyridinium

Tetrafluoroborate.” Journal of Physical Chemistry A

106, 3139–3147 (2002).

K.F. Chou, C.C. Han, and S. Lee, “Buffer Transport

in Hydroxyethyl Methacrylate Copolymer Irradiated by

Gamma-Rays.” Polymer 42, 4989–4996 (2001).

K.F. Chou, C.C. Han, and S. Lee, “Effect of Buffer

on the Optical Properties of Irradiated Hydroxyethyl

Methacrylate Copolymer.” Journal of Materials Research

17, 1199–1207 (2002).

J.F. Douglas, M.S. Kent, S.K. Satija, and A. Karim,

“Polymer Brushes: Structure and Dynamics.”

Encyclopedia of Materials: Science and Technology,

(in press).

M. Fernandez–Garcia and M.Y. Chiang, “Effect

of Hygrothermal Aging History on Sorption Process,

Swelling and Glass Transition Temperature in a ParticleFilled Epoxy-Based Adhesive.” Journal of Applied

Polymer Science 84, 1581–1591 (2002).

N. Gilra, C. Cohen, R.M. Briber, B.J. Bauer,

R.C. Hedden, and A.Z. Panagiotopoulos, “A SANS

Study of the Conformational Behavior of Linear

Chains in Compressed and Uncompressed End-Linked

Elastomers.” Macromolecules 34, 7773–7782 (2001).

S.D. Kim, E.M. Boczar, B.J. Bauer, A. Klein, and

L.H. Sperling, “A SANS Study of Sulfonate End Group

Effect on Polystyrene Self-Diffusion.” Polymeric

Materials: Science & Engineering 84, 605–606

(2001).

S.K. Kumar and J.F. Douglas, “Gelation in Physically

Associating Polymer Solutions.” Physical Review Letters

87, 8301–8304 (2001).

M.L. Mansfield and J.F. Douglas, “Numerical

Path-Integration Calculation of Transport Properties

of Star Polymers and Theta-DLA Aggregates.”

Condensed Matter Physics 5, 249–274 (2002).

N.S. Martys and J.F. Douglas, “Critical Properties

and Phase Separation in Lattice Boltzmann Fluid

Mixtures.” Physical Review E 63, 1205–1222

(2001).

Nanoscale Science, Engineering and Technology

K.A. Barnes, J.F. Douglas, D.W. Liu, and A. Karim,

“Influence of Nanoparticles and Polymer Branching on

the Dewetting of Polymer Films.” Advances in Colloid

and Interface Science 94, 83–104 (2001).

B.J. Bauer and E.J. Amis, “Characterization of

Dendritically Branched Polymers by Small Angle

Neutron Scattering (SANS), Small Angle X-Ray

Scattering (SAXS) and Transmission Electron

Microscopy (TEM).” Dendrimers and Other Dendritic

Polymers, pp. 255–284, D.A. Tomalia and J.M.J.

Frechet, eds., (John Wiley & Sons, Ltd., 2001).

B.J. Bauer and B.D. Viers, “Kinetics of Formation

of Many Armed Stars with Dendrimer Cores as a Model

of Crosslinking.” Polymeric Materials: Science &

Engineeering 84, 728–729 (2001).

R.A. Bubeck, B.J. Bauer, P. Dvornic, M.J. Owen,

S. Reeves, P. Parkham, and L.W. Hoffman, “SmallAngle Neutron Scattering from Metal Ion-Containing

PAMAMOS Dendrimer Networks.” Polymeric Materials:

Science & Engineering 84, 866–867 (2001).

R.D. Davis, J.W. Gilman, and D.L. VanderHart,

“Processing Degradation of Polyamide 6

Nanocomposites and Clay Organic Modifier.”

Polymer Degradation and Stability, (in press).

G. Evmenenko, B.J. Bauer, R. Kleppinger, B. Forier,

W. Dehaen, E.J. Amis, N. Mischenko, and H. Reynaers,

“The Influence of Molecular Architecture and Solvent

Type on the Size and Structure of Poly(Benzyl Ether)

Dendrimers by SANS.” Macromolecular Chemistry and

Physics 202, 891–899 (2001).

Polymers Division FY02 Annual Report Publication List
44

F. Grohn, B.J. Bauer, and E.J. Amis,

“Hydrophobically Modified Dendrimers as Inverse

Micelles: Formation of Cylindrical Multidendrimer

Nanostructures.” Macromolecules 34, 6701–6707

(2001).

F. Grohn, B.J. Bauer, G. Kim, and E.J. Amis,

“Nanoparticle Formation Within Dendrimer-Containing

Polymer Networks: Route to New Organic–Inorganic

Hybrid Materials.” Polymeric Materials: Science &

Engineering 84, 78–79 (2001).

F. Grohn, X.H. Gu, H. Grull, J.C. Meredith,

G. Nisato, B.J. Bauer, A. Karim, and E.J. Amis,

“Organization of Hybrid Dendrimer-Inorganic

Nanoparticles on Amphiphilic Surfaces.”

Macromolecules 35, 4852–4854 (2002).

F. Grohn, G. Kim, B.J. Bauer, and E.J. Amis,

“Nanoparticle Formation Within Dendrimer-Containing

Polymer Networks: Route to New Organic–Inorganic

Hybrid Materials.” Macromolecules 34, 2179–2185

(2001).

R.C. Hedden, B.J. Bauer, A.P. Smith, F. Groehn,

and E.J. Amis, “Templating of Inorganic Nanoparticles

by PAMAM/PEG Dendrimer-Star Polymers.”

Polymer, (in press).

G. Kim, F. Gröhn, B. Viers, B.J. Bauer,

C.L. Jackson, and E.J. Amis, “Dendritic Polymer

Templates for the Formation of Nanoparticles in Polymer

Matrix and their Characterization.” Proceedings of UKC,

June 24, 2002–June 28, 2002.

M.E. Mackay, Y. Hong, M. Jeong, S. Hong,

T.P. Russell, C.J. Hawker, R. Vestberg, and J.F. Douglas,

“Influence of Dendrimer Additives on the Dewetting of

Thin Polystyrene Films.” Langmuir 18, 1877–1882

(2002).

M.L. Mansfield, J.F. Douglas, and E.J. Garboczi,

“Intrinsic Viscosity and the Electric Polarizability of

Arbitrarily Shaped Objects.” Physical Review E 64,

1401–1416 (2001).

P.M. McGuiggan, S.M. Hsu, W. Fong, D. Bogy,

and C.S. Bhatia, “Friction Measurements of

Ultra-Thin Carbon Overcoats in Air.” Journal of

Tribology-Transactions of the ASME 124, 239–244

(2002).

T.J. Prosa, B.J. Bauer, and E.J. Amis, “From

Stars to Spheres: a Saxs Analysis of Dilute Dendrimer

Solutions.” Macromolecules 34, 4897–4906 (2001).

C.R. Snyder, J.P. Looney, and M.P. Casassa,

“Survey of FY 2001 Nanotechnology-Related Research

at the National Institute of Standards and Technology.”

NISTIR 6864, (2002).

D.L. Vanderhart, A. Asano, and J.W. Gilman,

“Solid-State NMR Investigation of Paramagnetic Nylon-6

Clay Nanocomposites. 1. Crystallinity, Morphology, and

the Direct Influence of Fe3+ on Nuclear Spins.”

Chemistry of Materials 13, 3781–3795 (2001).

D.L. Vanderhart, A. Asano, and J.W. Gilman,

“Solid-State NMR Investigation of Paramagnetic Nylon-6

Clay Nanocomposites. 2. Measurement of Clay Dispersion,

Crystal Stratification, and Stability of Organic Modifiers.”

Chemistry of Materials 13, 3796–3809 (2001).

Electronic Materials

Porous Low-k Dielectric Thin Films

B.J. Bauer, H.J. Lee, R.C. Hedden, D.W. Liu,

and W.L. Wu, “Pore Size Distributions in Low-k

Thin Films by X-Ray Reflectivity and Small Angle

Neutron Scattering.” Proceedings of the International

SEMATECH Ultra Low k Workshop, San Francisco,

June 6, 2002–June 7, 2002.

R.C. Hedden, B.J. Bauer, H.J. Lee, and W.L. Wu,

“Determination of Closed Pore Content in Nanoporous

Films by SANS Contrast Match.” ACS Polymeric

Materials Science and Engineering 87, 437 (2002).

H.J. Kim, W.L. Wu, B.J. Bauer, E.K. Lin, J.Y. Kim,

Y.H. Kim, and H.J. Lee, “Structural Characterization of

Porous Low-k SiOC Thin Films Using Novel X-Ray

Porosimetry.” IEEE International Conference on

Interconnect Technology, 2002.

H.J. Lee, E.K. Lin, H. Wang, W.L. Wu, W. Chen,

T.A. Deis, and E.S. Moyer, “Structural Comparison of

Hydrogen Silsesquioxane Based Porous Low-k Thin

Films Prepared With Varying Process Conditions.”

Chemistry of Materials 14, 1845–1852 (2002).

H.J. Lee, E.K. Lin, W.L. Wu, B.M. Fanconi,

J.K. Lan, Y.L. Cheng, H.C. Liou, Y.L. Wang,

M.S. Feng, and C.G. Chao, “X-Ray Reflectivity and

Ftir Measurements of N-2 Plasma Effects on the

Density Profile of Hydrogen Silsesquioxane Thin

Films.” Journal of the Electrochemical Society 148,

F195–F199 (2001).

H.J. Lee, C.L. Soles, D.W. Liu, B.J. Bauer,

and W.L. Wu, “X-ray Reflectivity as a Metrology

to Characterize Pore Size Distributions in Low-k

Dielectric Films.” ACS Polymer Materials: Science

and Engineering 87, 435 (2002).

H.J. Lee, C.L. Soles, D.W. Liu, B.J. Bauer, and

W.L. Wu, “Pore Size Distributions in Low-k Dielectric

Thin Films from X-ray Porosimetry.” Journal of Polymer

Science, Polymer Physics Edition, (in press).

Polymers Division FY02 Annual Report Publication List
45

E.K. Lin, H.J. Lee, B.J. Bauer, H. Wang, J.T. Wetzel,

and W.L. Wu, “Structure and Property Characterization

of Low-k Dielectric Porous Thin Films Determined by

X-ray Reflectivity and Small-angle Neutron Scattering.”

Low Dielectric Constant Materials for IC Applications,

P.S. Ho, J. Leu, and W.W. Lee, eds., (Springer

Publishing, Inc.), (in press).

E.K. Lin, H.J. Lee, G.W. Lynn, W.L. Wu, and

M.L. O’Neill, “Structural Characterization of A Porous

Low Dielectric Constant Thin Film with a Non-uniform

Depth Profile.” Applied Physics Letters 81, 607–609

(2002).

S. Yang, P. Mirau, C.S. Pai, O. Nalamasu,

E. Reichmanis, E.K. Lin, H.J. Lee, D. Gidley,

W.E. Frieze, T.L. Dull, J. Sun, and A.F. Yee, “Design

of Nanoporous Ultra Low-Dielectric Constant

Organosilicates by Self-Assembly.” Polymeric Materials:

Science & Engineering 84, 790–791 (2001).

S. Yang, P.A. Mirau, C.S. Pai, O. Nalamasu,

E. Reichmanis, E.K. Lin, H.J. Lee, D.W. Gidley, and

J.N. Sun, “Molecular Templating of Nanoporous

Ultralow Dielectric Constant (Approximate to 1.5)

Organosilicates by Tailoring the Microphase Separation

of Triblock Copolymers.” Chemistry of Materials 13,

2762–2764 (2001).

S. Yang, P.A. Mirau, C.S. Pai, O. Nalamasu,

E. Reichmanis, J.C. Pai, Y.S. Obeng, J. Seputro,

E.K. Lin, H.J. Lee, J.N. Sun, and D.W. Gidley,

“Nanoporous Ultralow Dielectric Constant

Organosilicates Templated by Triblock Copolymers.”

Chemistry of Materials 14, 369–374 (2002).

Polymers for Lithography

D.L. Goldfarb, M. Angelopoulos, E.K. Lin,

R.L. Jones, C.L. Soles, J.L. Lenhart, and W.L. Wu,

“Confinement Effects on the Spatial Extent of the

Reaction Front in Ultrathin Chemically Amplified

Photoresists.” Journal of Vacuum Science &

Technology B 19, 2699–2704 (2001).

J.L. Lenhart, R.L. Jones, E.K. Lin, C.L. Soles,

W.L. Wu, D.L. Goldfarb, and M. Angelopoulos,

“Combinatorial Methodologies Offer Potential for Rapid

Research of Photo-resist Materials and Formulations.”

Journal of Vacuum Science and Technology B 20,

704–709 (2002).

J.L. Lenhart, E.K. Lin, C.L. Soles, R.L. Jones,

W.L. Wu, D. Fischer, S. Sambasivan, D. Goldfarb,

and M. Angelopoulos, “Probing Surface and Bulk

Deprotection in Resist Films using NEXAFS.”

ACS Polymeric Materials Science and Engineering

87, 415 (2002).

E.K. Lin, R.L. Jones, W.L. Wu, J.G. Barker, P.J. Bolton,

and G.G. Barclay, “Structural Characterization of Deep

Sub-Micron Lithographic Structures using Small-Angle

Neutron Scattering.” Proceedings of SPIE, p. 4689,

Santa Clara, CA, March 4, 2002.

E.K. Lin, C.L. Soles, D.L. Goldfarb, B.C. Trinque,

S.D. Burns, R.L. Jones, J.L. Lenhart, M. Angelopoulos,

C.G. Willson, S.K. Satija, and W.L. Wu, “Direct

Measurement of the Reaction Front in Chemically

Amplified Photoresists with Nanometer Resolution.”

Science 297, 372–375 (2002).

E.K. Lin, C.L. Soles, D.L. Goldfarb, B.C. Trinque,

S.D. Burns, R.L. Jones, J.L. Lenhart, M. Angelopoulos,

C.G. Willson, S.K. Satija, and W.L. Wu, “Measurement

of the Spatial Evolution of the Deprotection Reaction

Front with Nanometer Resolution using Neutron

Reflectometry.” SPIE Proceedings — Advances in Resist

Processing and Technology XIX, 4690, Santa Clara, CA,

March 3, 2002–March 8, 2002.

V.M. Prabhu, R.L. Jones, E.K. Lin, J.L. Lenhart,

C.L. Soles, W.L. Wu, D.L. Goldfarb, and

M. Angelopoulos, “Reaction Front Induced Roughness

in Chemically Amplified Photoresists.” ACS Polymeric

Materials: Science and Engineering 87, 418 (2002).

C.L. Soles, E.K. Lin, J.L. Lenhart, R.L. Jones,

W.L. Wu, D.L. Goldfarb, and M. Angelopoulos, “Thin

Film Confinement Effects on the Thermal Properties

of Model Photoresist Polymers.” Journal of Vacuum

Science & Technology B 19, 2690–2693 (2001).

Dielectric Characterization/Electronics Packaging

C.K. Chiang, L.P. Sung, and R. Popielarz,

“Investigation of Morphology and Interface in Polymer

Composite Thin Films.” Materials Research Society

Symposium Proceedings 665, C5.27.1–5, 2001.

N. Noda and J. Obrzut, “High Frequency Dielectric

Relaxation in Polymers Filled With Ferroelectric

Ceramics.” Materials Research Society Symposium

Proceedings 698, E3.8.1–6, 2002.

J. Obrzut, “Dielectric Characterization of

Embedded Decoupling Capacitance Films at Microwave

Frequencies.” SMTA International Conference, New

and Emerging Technologies, pp. 49–54, Dallas TX,

October 31, 2000–November 2, 2000.

Obrzut J., “High Frequency Input Impedance

Characterization of Dielectric Films for Power-Ground

Planes.” IEEE Instrumentation and Measurements

Technology Conference, IMTC/2002, Proceedings of

the 19th IEEE, 2, pp. 1341–1343, May 23, 2002.

J. Obrzut, N. Noda, and R. Nozaki, “Broadband

Dielectric Metrology for Polymer Composite Films.”

2001 Annual Report: Conference on Electrical

Insulation and Dielectric Phenomena, pp. 269–272,

2001.

R. Popielarz, C.K. Chiang, R. Nozaki, and J. Obrzut,

“Dielectric Properties of Polymer/Ferroelectric Ceramic

Composites From 100 Hz to 10 Ghz.” Macromolecules

34, 5910–5915 (2001).

Polymers Division FY02 Annual Report Publication List
46

C.R. Snyder and F.I. Mopsik, “NIST Recommended

Practice Guide: Capacitance Cell Measurement of the

Out-of-Plane Expansion of Thin Films.” NIST Special

Publication 960–7 (2001).

C.R. Snyder and F.I. Mopsik, “A Precision

Capacitance Cell for Measurement of Thin Film

Out-of-Plane Expansion — Part III: Conducting

and Semiconducting Materials.” IEEE Transactions

on Instrumentation and Measurement 50, 1212–1215

(2001).

Polymer Thin Film Fundamentals

M.Y. Chiang, C.K. Chiang, and W.L. Wu,

“A Technique for Deducing In-Plan Modulus and

Coefficient of Thermal Expansion of a Supported Thin

Film.” Journal of Engineering Materials and Technology

124, 274–277 (2002).

D.S. Fryer, R.D. Peters, E.J. Kim, J.E. Tomaszewski,

J.J. De Pablo, P.F. Nealey, C.C. White, and W.L. Wu,

“Dependence of the Glass Transition Temperature of

Polymer Films on Interfacial Energy and Thickness.”

Macromolecules 34, 5627–5634 (2001).

J.L. Lenhart and W.L. Wu, “Deviations in the

Thermal Properties of Ultrathin Polymer Network

Films.” Macromolecules 35, 5145–5152 (2002).

G.W. Lynn, M.D. Dadmun, W.L. Wu, E.K. Lin,

and W.E. Wallace, “Neutron Reflectivity Studies of the

Interface Between a Small Molecule Liquid Crystal and

a Polymer.” Liquid Crystals 29, 551–557 (2002).

K.L. Ngai, L.R. Bao, A.F. Yee, and C.L. Soles,

“Correlation of Positron Annihilation and Other

Dynamic Properties in Small Molecular Glass-forming

Substances.” Physical Review Letters 87, 5901–5904

(2001).

D.J. Pochan, E.K. Lin, and W.L. Wu, “Surface

Directed Crystallization and Autophobic Dewetting in

Semicrystalline Polymer Thin Films.” Macromolecules,

(in press).

A.C. Powell, W.E. Wallace, D. Wheeler, J. Warren,

and D. Josell, “Misaligned Flip-Chip Solder Joints:

Prediction and Experimental Determination of Lateral

and Normal Force-Displacement Curves.” Journal of

Electronic Packaging, (in press).

Y. Pu, M.H. Rafailovich, J. Sokolov, D. Gersappe,

T. Peterson, W.L. Wu, and S.A. Schwarz, “Mobility of

Polymer Chains Confined at a Free Surface.” Physical

Review Letters 87, 6101–6104 (2001).

Y. Pu, H. White, M. Rafailovich, J. Sokolov,

A. Patel, C. White, W.L. Wu, V. Zaitsev, and S. Schwarz,

“Probe Diffusion in Thin PS Free-Standing Films.”

Macromolecules 34, 8518–8522 (2001).

C.L. Soles, J.F. Douglas, W.L. Wu, and R.M. Dimeo,

“The Dynamics of Confined Polycarbonate Chains

Probed with Incoherent Neutron Scattering.” Polymeric

Materials: Science & Engineering 85, 81–82 (2001).

C.L. Soles, J.F. Douglas, W.L. Wu, and R.M. Dimeo,

“Incoherent Neutron Scattering and the Dynamics of

Confined Polycarbonate Films.” Physical Review Letters

88, 7401–7404 (2002).

C.L. Soles, J.F. Douglas, W.L. Wu, H. Peng, and

D.W. Gidley, “A Broad Perspective on the Dynamics of

Highly Confined Polymer Films.” MRS Conference

Proceedings, 2002.

W.E. Wallace, J. Warren, D. Josell, and D. Wheeler,

“Prediction of Lateral and Normal Force-Displacement

Curves for Flipchip Solder Joints.” Computational

Modeling of Materials, Minerals, and Metals

Processing, p. 663, M. Cross, J.W. Evans, and

C. Bailey, eds., (2002).

C.C. White, K.B. Migler, and W.L. Wu, “Measuring

T-G in Ultra-Thin Polymer Films With an Excimer

Fluorescence Technique.” Polymer Engineering and

Science 41, 1497–1505 (2001).

Biomaterials

Dental Materials

J.M. Antonucci, B.O. Fowler, S.H. Dickens,

and N.D. Richards, “Novel Dental Resins from

Trialkoxysilanes and Dental Monomers by

in-situ Formation of Oligomeric Silyl Ethers and

Silsesquioxanes.” ACS Polymer Preprints, 43,

(in press).

J.M. Antonucci, W.G. McDonough, D.W. Liu, and

D. Skrtic, “Effect of Polymer Matrices on Methacrylate

Conversion and Mechanical Strength of Bioactic

Composites Based on Amorphous Calcium Phosphate.”

ACS Polymer Preprints, 43, (in press).

J.M. Antonucci, D. Skrtic, and R.T. Brunworth,

“Methacrylate Conversion in Photo-polymerized

Composites Containing Amorphous Calcium Phosphate

Fillers.” Polymeric Materials: Science & Engineering 85,

55–56 (2001).

J.M. Antonucci, D. Skrtic, A.W. Hailer, and

E.D. Eanes, “Bioactive Polymeric Composites Based

on Hybrid Amorphous Calcium Phosphates.” Polymeric

Drugs & Drug Delivery Systems, pp. 301–310,

R.M. Ottenbrite and S.W. Kim, eds., (Technomics

Publishing Company, Inc., Lancaster, PA 2001).

S.H. Dickens, J.M. Antonucci, and B.O. Fowler,

“Evaluation of the Interactions of a Silane Agent with

Dental Monomers by Near Infrared Spectroscopy.”

ACS Polymer Preprints, 43, (in press).

Polymers Division FY02 Annual Report Publication List
47

H.H.K. Xu, F.C. Eichmiller, D.T. Smith,

G.E. Schumacher, A.A. Giuseppetti, and J.M. Antonucci,

“Effect of Thermal Cycling on Whisker-reinforced

Dental Resin Composites.” Journal of Materials Science

— Materials in Medicine 13, 875–883 (2002).

C.A. Khatri, J.M. Antonucci, and G.E. Schumacher,

“Self-Etching, Polymerization-Initiating Primers for

Dental Adhesion.” Polymeric Drugs & Delivery Systems,

pp. 289–300, R.M. Ottenbrite and S.W. Kim, eds.,

(Technomics Publishing Company, Inc., Lancaster, PA,

2001).

C.C. Khatri, J.W. Stansbury, C.R. Schultheisz,

and J.M. Antonucci, “Synthesis, Characterization and

Evaluation of Urethane Derivatives of Bis-GMA.”

Dental Materials, (in press).

K. Komatsu, F.W. Wang, and K. Nemoto,

“Novel Fluorescence Method for Cure Monitoring

of Photo-Cured Composites.” Journal of Dental

Research 81, 259 (2002).

W.G. McDonough, J.M. Antonucci, J. He,

Y. Shimada, M.Y. Chiang, G. Schumacher, and

C.R. Schultheisz, “A Microshear Test to Measure

Bond Strengths of Dentin-Polymer Interfaces.”

Biomaterials 23, 3603–3608 (2002).

D. Skrtic, J.M. Antonucci, and E.D. Eanes,

“Effect of the Monomer and Filler Systems on the

Remineralizing Potential of Bioactive Dental Composites

Based on Amorphous Calcium Phosphate.” Polymers for

Advanced Technologies 12, 369–379 (2001).

D. Skrtic, J.M. Antonucci, E.D. Eanes, and

R.T. Brunworth, “Silica- and Zirconia-Hybridized

Amorphous Calcium Phosphate: Effect on

Transformation to Hydroxyapatite.” Journal of

Biomedical Materials Research 59, 597–604 (2002).

H.H.K. Xu, J.B. Quinn, D.T. Smith, J.M. Antonucci,

G.E. Schumacher, and F.C. Eichmiller, “Dental Resin

Composites Containing Silica-Fused Whiskers — Effects

Of Whisker-To-Silica Ratio On Fracture Toughness

And Indentation Properties.” Biomaterials 23, 735–742

(2002).

Tissue Engineering Methodology

D.S. Bright, F.W. Wang, C.A. Khatri, S. Yoneda,

and W.F. Guthrie, “Effects of Hydrolytic Degradation

on In Vitro Biocompatibility of Poly (d,l-lactic acid).”

Journal of Dental Research 81, 186 (2002).

C.A. Khatri, J.F. Hsii, and F.W. Wang, “Moldable

Composite Bone Grafts Consisting of Calcium

Phosphate Cement and Biodegradable Polymer

Microspheres: Mechanical Properties and Controlled

Release of Bioactive Molecules.” Transactions of the

28th Annual Meeting of the Society for Biomaterials,

728, Tampa, FL, April 2002.

C.G. Simon, C.A. Khatri, S.A. Wight, and

F.W. Wang, “Preliminary Report on the Biocompatibility

of a Moldable, Resorbable, Composite Bone Graft

Consisting of Calcium Phosphate Cement and

Poly(Lactide-Co-Glycolide) Microspheres.” Journal of

Orthopaedic Research 20, 473–482 (2002).

C.G. Simon Jr and F.W. Wang, “Seeding Cells

into Calcium Phosphate Cement.” Transactions of the

28th Meeting of the Society for Biomaterials, p. 222,

Tampa, FL, April 2002.

F.W. Wang, C.A. Khatri, J.F. Hsii, S. Hirayama, and

S. Takagi, “Polymer-Filled Calcium Phosphate Cement:

Mechanical Properties and Controlled Release of

Growth Factor.” Biomedical Engineering: Recent

Developments, J. Vossoughi, ed., (in press).

N.R. Washburn, J.P. Dunkers, A. Karim, and E.J.

Amis, “Polymer Processing and Tissue Engineering.”

Society for Biomaterials 2001 Annual Meeting, 199,

St. Paul, MN, 2001.

N.R. Washburn, C.G. Simon, A. Tona,

H.M. Elgendy, A. Karim, and E.J. Amis, “Co-Extrusion

of Biocompatible Polymers for Scaffolds With

Co- Continuous Morphology.” Journal of Biomedical

Materials Research 60, 20–29 (2002).

M.D. Weir, J.M. Antonucci, and F.W. Wang,

“Rapid Screening of the Lower Critical Solution

Temperature of Injectable Hydrogels for Tissue

Engineering Applications.” Transactions of the 28th

Annual Meeting of the Society for Biomaterials, 168,

Tampa, FL, April 2002.

M.D. Weir, C.A. Khatri, and J.M. Antonucci,

“Facile Synthesis of Hydroxylated Dimethacrylates

for Use in Biomedical Applications.” ACS Polymer

Preprints 42, 131–132 (2001).

Characterization

G. Caliskan, A. Kisliuk, A.M. Tsai, C.L. Soles, and

A.P. Sokolov, “Influence of Solvent on Dynamics and

Stability of a Protein.” Journal of Non-Crystalline Solids

387, 307–310 (2002).

J.A. Coddington, H.D. Henri, D. Chanzy,

C.L. Jackson, G. Raty, and K.H. Gardner, “The Unique

Ribbon Morphology of the Major Ampullate Silk of

Spiders from the Genus Loxosceles (Recluse Spiders).”

Biomacromolecules 3, 5–8 (2002).

K. Efimenko, W.E. Wallace, and J. Genzer,

“Modification of Silicon Rubber Surfaces.” Chemistry

of Materials, (in press).

J. Parkas, M. Paulsson, D.L. VanderHart, and

U. Westermark, “Accelerated Light-Induced Aging of

alpha-, beta-, and gamma-C13-enriched Cell Wall

Dehydrogenation Polymers Studied with Solid State

C13 NMR Spectroscopy.” Journal of Wood Chemistry

and Technology, (in press).

Polymers Division FY02 Annual Report Publication List
48

N. Terashima, J. Hafren, U. Westermark, and

D.L. Vanderhart, “Nondestructive Analysis of Lignin

Structure by NMR Spectroscopy of Specifically

C-13-Enriched Lignins Part 1. Solid State Study of

Ginkgo Wood.” Holzforschung 56, 43–50 (2002).

F.W. Wang and D.G. Sauder, “Examination of

Fluorescent Molecules as in situ Probes of

Polymerization Reactions.” Polymeric Drugs & Drug

Delivery Systems, pp. 279–287, R.M. Ottenbrite and

S.W. Kim, eds., (Technomic Publishing Co., Inc.,

Lancaster, PA, 2001).

Multiphase Materials

Blends

Y.A. Akpalu, A. Karim, S.K. Satija, and N.P. Balsara,

“Suppression of Lateral Phase Separation in Thin

Polyolefin Blend Films.” Macromolecules 34,

1720–1729 (2001).

J. Dudowicz, K.F. Freed, and J.F. Douglas,

“Beyond Flory–Huggins Theory: New Classes

of Blend Miscibility Associated With Monomer

Structural Asymmetry.” Physical Review Letters 88,

5503–5506 (2002).

J. Dudowicz, K.F. Freed, and J.F. Douglas, “New

Patterns of Polymer Blend Miscibility Associated

With Monomer Shape and Size Asymmetry.” Journal

of Chemical Physics 116, 9983–9996 (2002).

A.R. Esker, H. Grull, G. Wegner, S.K. Satija, and

C.C. Han, “Isotopic Selectivity in Ultrathin Langmuir–

Blodgett Membranes of a Cross-Linked Cellulose

Derivative.” Langmuir 17, 4688–4692 (2001).

H. Gruell, L. Sung, A. Karim, J.F. Douglas,

S.K. Satija, and C.C. Han, “Surface Segregation of a

Symmetrical Segregating Polymer Blend Film Above

and Below the Critical Point of Phase Separation.”

Europhys. Lett., (in press).

C.C. Han, H. Wang, K. Shimizu, H. Kim, E.

Hobbie, and Z.G. Wang, “Structure Development from

Simultaneous Phase Separation and Crystallization of a

Metallocene Polyolefin Blend.” ACS Polymer Preprints,

(in press).

M. Hayashia, T. Hashimoto, M. Weber, H. Grull,

A.R. Esker, C.C. Han, and S.K. Satija, “Transient

Interfacial Instability in Bilayer Polymer Films as

Observed by Neutron Reflectivity Studies.” Polymer

42, 9771–9782 (2001).

E.K. Hobbie, H.S. Jeon, H. Wang, H. Kim, and

C.C. Han, “Shear-Induced Structure in Polymer Blends

with Viscoelastic Asymmetry.” Journal of Chemical

Physics, (in press).

J. Hwang, L.S. Goldner, A. Karim, and C. Gettinger,

“Imaging Phase-Separated Domains in Conducting

Polymer Blend Films With Near-Field Scanning Optical

Microscopy.” Applied Optics 40, 3737–3745 (2001).

U. Jeng, T.L. Lin, W.J. Liu, C.S. Tsao,

T. Canteenwala, L.Y. Chiang, L.P. Sung, and C.C. Han,

“SANS and SAXS Study on Aqueous Mixtures of

Fullerene-Based Star Ionomers and Sodium Dodecyl

Sulfate.” Physica A 304, 191–201 (2002).

H.S. Jeon and E.K. Hobbie, “Erratum: Shear

Viscosity of Phase-Separating Polymer Blends with

Viscous Asymmetry [PRE 63, 061403 (2001)].”

Physical Review E 64, 9901 (2001).

H.S. Jeon, S. Kim, and C.C. Han, “Phase

Separation Induced by Shear Quenching in Polymer

Blends With a Diblock Copolymer.” Journal of Polymer

Science Part B — Polymer Physics 39, 819–830

(2001).

H.S. Jeon, Z. Shou, A. Chakrabati, and

E.K. Hobbie, “Anisotropic Ordering in Sheared

Binary Fluids with Viscous Asymmetry: Experiment

and Computer Simulation.” Physical Review E 65,

1508 (2002).

Y. Jiang, A. Saxena, T. Lookman, and J.F. Douglas,

“Influence of Filler Particles and Clusters on Phase

Separation in Binary Polymer Blends.” Journal of the

Materials Research Society, (in press).

A. Karim, J.F. Douglas, K.A. Barnes, A.I. Nakatani,

D.W. Liu, and E.J. Amis, “Studies of Polymer-filler

Interactions in Filled Systems.” ACS Polymer Preprints

42, 25–26 (2001).

A. Karim, J.F. Douglas, L.P. Sung, and B.D. Ermi,

“Self-assembly by Phase Separation in Polymer Thin

Films.” Encyclopedia of Materials Science and Technology,

(2001).

G. Kim, C.C. Han, M. Libera, and C.L. Jackson,

“Crystallization Within Melt Ordered Semicrystalline

Block Copolymers: Exploring the Coexistence of

Microphase-Separated and Spherulitic Morphologies.”

Macromolecules 34, 7336–7342 (2001).

A.I. Nakatani, W. Chen, R.G. Schmidt, G.V. Gordon,

and C.C. Han, “Chain Dimensions in Polysilicate-Filled

Poly(Dimethyl Siloxane).” International Journal of

Thermophysics 23, 199–209 (2002).

A.I. Nakatani, R. Ivkov, P. Papanek, C.L. Jackson,

H. Yang, L. Nikiel, and M. Gerspacher, “The Significance

of Percolation on the Dynamics of Polymer Chains

Bound to Carbon Black.” Materials Research Society

Symposium Proceedings 661, KK4.2.1–4.2.6 (2001).

Polymers Division FY02 Annual Report Publication List
49

F.W. Starr and S.C. Glotzer, “Simulation of Filled

Polymer Melts on Multiple Length Scales.” Materials

Research Society Symposium Proceedings 661,

KK4.1.1–4.1.13 (2001).

F.W. Starr, T.B. Schroder, and S.C. Glotzer,

“Effects of a Nanoscopic Filler on the Structure

and Dynamics of a Simulated Polymer Melt and the

Relationship to Ultrathin Films.” Physical Review E 64,

1802–1805 (2001).

G.Z.G. Wang, H. Wang, K. Shimizu, C.C. Han,

and B.S. Hsiao, “Early Stage Crystallization in Poly

(Ethylene-co-Hexene) by SAXS/WAXD, DSC, OM

and AFM.” Polymeric Materials: Science & Engineering

85, 435–436 (2001).

H. Wang, R.J. Composto, E.K. Hobbie, and

C.C. Han, “Multiple Lateral Length Scales in

Phase-Separating Thin-Film Polymer Blends.”

Langmuir 17, 2857–2860 (2001).

H. Wang and C.C. Han, “Silica Nano-particle Filled

Poly(ethylene-ran-hexene)/xylene Gels.” Materials

Research Society Symposium Proceedings 661,

KK8.13.1–8.13.13 (2001).

H. Wang, K. Shimizu, E.K. Hobbie, Z.G. Wang,

J.C. Meredith, A. Karim, E.J. Amis, B.S. Hsiao,

E.T. Hsieh, and C.C. Han, “Phase Diagram of a Nearly

Isorefractive Polyolefin Blend.” Macromolecules 35,

1072–1078 (2002).

H. Wang, K. Shimizu, H.W. Kim, E.K. Hobbie,

G.Z. Wang, and C.C. Han, “Competing Growth Kinetics

in Simultaneously Crystallizing and Phase-Separating

Polymer Blends.” Journal of Chemical Physics 116,

7311–7315 (2002).

H. Wang, G.Z.G. Wang, C.C. Han, and

B.S. Hsiao, “Simultaneous SAXS and WAXS Study

of the Isothermal Crystallization in Polyolefin Blends.”

ACS Polymeric Materials Science and Engineering

85, 427–428 (2001).

Z.G. Wang, X.H. Wang, B.S. Hsiao, S. Andjelic,

D. Jamiolkowski, J. Mcdivitt, J. Fischer, J. Zhou, and

C.C. Han, “Time-Resolved Isothermal Crystallization

of Absorbable Pga-Co-Pla Copolymer by Synchrotron

Small-Angle X-Ray Scattering and Wide-Angle X-Ray

Diffraction.” Polymer 42, 8965–8973 (2001).

Z.G. Wang, X.H. Wang, B.S. Hsiao, R.A. Phillips,

F.J. Medellin-Rodriguez, S. Srinivas, H. Wang, and

C.C. Han, “Structure and Morphology Development

in Syndiotactic Polypropylene During Isothermal

Crystallization and Subsequent Melting.” Journal of

Polymer Science Part B — Polymer Physics 39,

2982–2995 (2001).

Composites

M.Y. Chiang and M. Fernandez-Garcia, “Relation

of Swelling and Tg Depression to the Apparent Free

Volume of a Particle-Filled Epoxy-based Adhesive.”

Journal of Applied Polymer Science, (in press).

M.Y.M. Chiang and J. He, “V-notch Shear

Testing for Hybrid Fiber Composites — An Analytical

Assessment.” Journal of Composite Materials, (in press).

J.P. Dunkers, K.M. Flynn, R.S. Parnas, and

D.D. Sourlas, “Model-Assisted Feedback Control for

Liquid Composite Molding.” Composites Part A —

Applied Science and Manufacturing 33, 841–854

(2002).

J.P. Dunkers, D.P. Sanders, D.L. Hunston,

M.J. Everett, and W.H. Green, “Comparison of Optical

Coherence Tomography, X-Ray Computed Tomography,

and Confocal Microscopy Results From an Impact

Damaged Epoxy/E-Glass Composite.” Journal of

Adhesion 78, 129–154 (2002).

J.M. He, M.Y. Chiang, and D.L. Hunston,

“Assessment of Sandwich Beam in Three-Point Bending

for Measuring Adhesive Shear Modulus.” Transactions

of the ASME, Journal of Engineering Materials and

Technology 123, 322–328 (2001).

G.A. Holmes, R.C. Peterson, D.L. Hunston, and

W.G. McDonough, “E-Glass/DGEBA/m-PDA Single

Fiber Composites: Interface Debonding During Fiber

Fracture.” Polymer Composites, (in press).

D.L. Hunston, “Analyzing Load History Dependence

of Fracture in Structural Adhesives: History Lesson.”

Adhesives Age 44, 35–42 (2001).

D.L. Hunston, Z. Miyagi, C.R. Schultheisz,

S. Zaghi, and H. Binson, “Sandwich Bending Specimen

for Characterizing Adhesive Properties.” Mechanics of

Time-Dependent Materials, (in press).

J.L. Lenhart, J.H. van Zanten, J.P. Dunkers, and

R.S. Parnas, “Fluorescent Characterization of Silane

Layers and the Buried Interfacial Chemistry.” Journal of

Colloid and Interface Science, (in press).

J.L. Lenhart, J.H. van Zanten, J.P. Dunkers, and

R.S. Parnas, “Using a Localized Fluorescent Dye

to Probe the Glass/Resin Interphase.” Polymer

Composites, (in press).

B.S. Majumdar and D.L. Hunston, “Continuous

Parallel Fiber Composites: Fracture.” Encyclopedia of

Materials: Science and Technology, pp. 1618–1629,

(Elsevier Science Ltd., Oxford, England, 2001).

W.G. McDonough, J.P. Dunkers, G.A. Holmes,

E. Feresenbet, Y.H. Kim, and R.S. Parnas, “Influence

of Processing Rate and Formulation on the Interface

Strength of Vinyl Ester/E-Glass Composites.” Polymer

Composites 23, 274–283 (2002).

Polymers Division FY02 Annual Report Publication List
50

K.M. Pillai, C.L. Tucker, and F.R. Phelan,

“Numerical Simulation of Injection/Compression Liquid

Composite Molding. Part 2: Preform Compression.”

Composites Part A — Applied Science and

Manufacturing 32, 207–220 (2001).

D. Raghavan, J. He, D.L. Hunston, and

D. Hoffman, “Strain Rate Dependence of Fracture

in a Rubber-Toughened Epoxy System.” Journal of

Adhesion, (in press).

Filled Polymers

V. Ferreiro, G. Schmidt, C.C. Han, and A. Karim,

“Dispersion and Nucleating Effects of Clay Fillers in

Nanocomposite Polymer Films.” Polymer Preprints,

(in press).

S.C. Glotzer and F.W. Starr, “Multiscale Modeling

of Filled and Nanofilled Polymers.” Proceedings of

Foundations of Molecular Modeling and Simulation,

(in press).

C.C. Han, G. Schmidt, A.I. Nakatani, and P. Butler,

“A Small Angle Neutron Scattering Study on Polymer

Clay Solutions,” Polymeric Materials: Science &

Engineering 85, 219–220 (2001).

C.C. Han, G. Schmidt, A.I. Nakatani, and

A. Karim, “Characterization of Polymer-Clay Solutions

by Rheology, Flow Birefringence and SANS.”

ACS Polymer Preprints 42, 269–270 (2001).

E.K. Hobbie, F.W. Starr, J.F. Douglas, and

C.C. Han, “Bridging the Gap between Structure and

Properties in Nano-Particle Filled Polymers.” NISTIR

6893 (2002).

S. Lin–Gibson, G. Schmidt, J. Pathak, and

C.C. Han, “Rheology of Poly(ethylene oxide) Clay

Solutions.” ACS Polymeric Materials Science and

Engineering, (in press).

A.B. Morgan, J.W. Gilman, and C.L. Jackson,

“Characterization of the Dispersion of Clay in a

Polyetherimide Nanocomposite.” Macromolecules

34, 2735–2738 (2001).

G. Schmidt, A.I. Nakatani, P.D. Butler, and

C.C. Han, “Small-Angle Neutron Scattering From

Viscoelastic Polymer-Clay Solutions.” Macromolecules

35, 4725–4732 (2002).

G. Schmidt, A.I. Nakatani, and C.C. Han, “Rheology

and Flow-Birefringence From Viscoelastic Polymer-Clay

Solutions.” Rheologica Acta 41, 45–54 (2002).

F.W. Starr, T.B. Schroder, and S.C. Glotzer,

“Molecular Dynamics Simulation of a Polymer Melt

With a Nanoscopic Particle.” Macromolecules 35,

4481– 4492 (2002).

Processing Characterization

Microscale Processing

J.A. Pathak, M.C. Davis, S.D. Hudson, and

K.B. Migler, “Layered Droplet Microstructures in

Sheared Emulsions: Finite-Size Effects.” Journal of

Colloid and Interface Science, (in press).

J.A. Pathak, S.D. Hudson, and K.B. Migler,

“Structure Formation in Micro-Confined Polymeric

Emulsions.” ACS Polymer Preprints, (in press).

Process Monitoring

A.J. Bur and S.C. Roth, “Real-Time Monitoring of

Fluorescence Anisotropy and Temperature During

Processing of Biaxially Stretched Polypropylene Film.”

Proceedings of the Society of Plastics Engineers Annual

Technical Conference, San Francisco, CA, May 2002.

A.J. Bur, S.C. Roth, and H. Lobo, “Temperature

Effects During Capillary Rheometry Testing.” Proceedings

of the Society of Plastics Engineers Annual Technical

Conference, San Francisco, CA, May 2002.

A.J. Bur, S.C. Roth, and M. McBrearty,

“In-Line Dielectric Monitoring During Extrusion of

Filled Polymers.” Review of Scientific Instruments

73, 2097–2102 (2002).

A.J. Bur, M.G. Vangel, and S.C. Roth, “Fluorescence

Based Temperature Measurements and Applications to

Real-Time Polymer Processing.” Polymer Engineering

and Science 41, 1380–1389 (2001).

A.J. Bur, M.G. Vangel, and S.C. Roth, “Temperature

Dependence of Fluorescent Probes for Applications to

Polymer Materials Processing.” Applied Spectroscopy

56, 174–181 (2002).

M. McBrearty, A.J. Bur, and S.C. Roth, “Variation

of Electrical Properties with Exfoliation Condition in

Nanocomposites.” Proceedings of the Society of

Plastics Engineers Annual Technical Conference,

San Francisco, CA, May 2002.

Multivariant Measurement Methods

Combinatorial Methods Development

K.M. Ashley, A. Sehgal, E.J. Amis, D. Raghavan,

and A. Karim, “Combinatorial Mapping of Polymer

Film Wettability on Gradient Energy Surfaces.”

Materials Research Society Symposium Proceedings

on Organic/Biological Materials and Devices:

Polymeric Interfaces and Thin Films, (in press).

A.J. Crosby, A. Karim, and E.J. Amis,

“Combinatorial Investigations of Polymer Adhesion.”

ACS Polymer Preprints 42, 645–646 (2001).

Polymers Division FY02 Annual Report Publication List
51

C.H. Davis, A. Karim, K.L. Beers, A.J. Crosby,

A.P. Smith, and E.J. Amis, “Polymer Science at the

NIST Combinatorial Methods Center.” ACS Polymeric

Materials Science and Engineering 87, 239 (2002).

A. Karim, A. Sehgal, J.C. Meredith, and E.J. Amis,

“Combinatorial Mapping of Polymer Blends Phase

Behavior.” Experimental Design for Combinatorial and

High Throughput Materials Science, Ch. 5., J. Cawse,

ed., (John Wiley & Sons, Ltd.), (in press).

A. Karim, K. Yurekli, C. Meredith, E.J. Amis, and

R. Krishnamoorti, “Combinatorial Methods for Polymer

Science: Phase Behavior of Nanocomposite Blend

Films.” Polymer Engineering and Science.

J.C. Meredith, A. Karim, and E.J. Amis,

“Combinatorial Methods for Investigations in Polymer

Materials Science.” MRS Bulletin 27, 330 (2002).

J.C. Meredith, A.P. Smith, A. Karim, and E.J. Amis,

“Combinatorial Polymer Science: Synthesis and

Characterization.” ACS Symposium Series Book

Chapter, (in press).

J.C. Meredith, A.P. Smith, A. Tona, H. Elgendy,

A. Karim, and E.J. Amis, “Combinatorial Characterization

of Complex Polymers: Thin Film and Biomedical

Polymers.” Polymeric Materials: Science & Engineering

84, 1065–1066 (2001).

S.V. Roberson, A. Sehgal, A.J. Fahey, and A. Karim,

“Time-of-Flight Secondary Ion Mass Spectrometry

(ToF-SIMS) for High-Throughput Characterization

of Bio-Surfaces.” Applied Surface Science 9375, 1–4

(2002).

A. Sehgal, A. Karim, and E.J. Amis, “NIST

Combinatorial Methods Center, July 10, 2001:

Meeting Proceedings.” NISTIR 6804 (2001).

C.M. Stafford, C. Harrison, A. Karim, and

E.J. Amis, “Measuring Modulus of Gradient Polymer

Films by Strain-Induced Bucking Instabilities.”

ACS Polymer Preprints, (in press).

Surface and Polymer Interactions

A. Sehgal, V. Ferreiro, J.F. Douglas, E.J. Amis, and

A. Karim, “Spinodal Dewetting on Chemically Patterned

Substrates.” Langmuir, (in press).

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

and A. Karim, “Combinatorial Study of Surface Pattern

Formation in Thin Block Copolymer Films.” Physical

Review Letters 8701, 5503–5504 (2001).

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

and A. Karim, “High-Throughput Characterization of

Pattern Formation in Symmetric Diblock Copolymer

Films.” Journal of Polymer Science Part B — Polymer

Physics 39, 2141–2158 (2001).

A.P. Smith, A. Sehgal, E.J. Amis, and A. Karim,

“Characterization of Surface Energy Effects on

Morphology of Thin Diblock Copolymer Films by High

Throughput Techniques.” ACS Polymer Preprints 42,

641–642 (2001).

K. Yurekli, R. Krishnamoorti, and A. Karim,

“Phase Behavior of Polymer Nanocomposite Thin

Films.” Polymeric Materials: Science & Engineering 85,

256–257 (2001).

Polymers Division FY02 Annual Report Publication List
52
53

Polymers Division

Polymers Division

Chief

Eric J. Amis

Phone: 301–975–6762

E-mail: eric.amis@nist.gov

Deputy Chief

Chad R. Snyder

Phone: 301–975–4526

E-mail: chad.snyder@nist.gov

NIST Fellows

Charles C. Han

Phone: 301–975–6772

E-mail: charles.han@nist.gov

Group Leaders

Characterization and Measurement —

Method Development

Wen-li Wu

Phone: 301–975–6839

E-mail: wen-li.wu@nist.gov

Standards and Data

Bruno M. Fanconi

Phone: 301–975–6769

E-mail: bruno.fanconi@nist.gov

Internal Capabilities

Chad R. Snyder

Electronics Materials

Eric K. Lin

Phone: 301–975–6743

E-mail: eric.lin@nist.gov

Biomaterials

Eric J. Amis, Acting

Multiphase Materials

Charles Han

Processing Characterization

Kalman Migler

Phone: 301–975–4876

E-mail: kalman.migler@nist.gov

Multivariant Measurement Method

Alamgir Karim

Phone: 301–975–6588

E-mail: alamgir.karim@nist.gov
54

Research Staff

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

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

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

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

Amis, Eric J.

eric.amis@nist.gov

Neutron, x-ray and light scattering

Polyelectrolytes

Viscoelastic behavior of polymers

Dendrimers and dendritic polymers

Functional biomaterials

Anopchenko, Oleksiy S.

oleksiy.anopchenko@nist.gov

Dielectric relaxation spectroscopy

X-ray scattering

Microwave spectroscopy techniques

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

Porous low-k thin film characterization

Beers, Kathryn

kathryn.beers@nist.gov

Crystallization in thin films

Optical light scattering

Controlled/living polymerizations

Bencherif, Sidi

sidi.bencherif@nist.gov

Mass spectrometry

Chemical modification

Research Staff
55

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

Cicerone, Marcus T.

marcus.cicerone@nist.gov

Protein stabilization

Glass transition theory

Optical coherence tomography

Confocal microscopy

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

Davis, Cher

cher.davis@nist.gov

NIST Combinatorial Methods Center

Polymer nanocomposites

Polymers synthesis

Combinatorial methods and measurements

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

Conductivity/viscosity of nanoparticle filled

 systems

Crystallization of polymers

Duan, Hu +

hu.duan@nist.gov

Electron microscopy

Self-assembly and liquid crystals

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
56

Research Staff

Fanconi, Bruno M.

bruno.fanconi@nist.gov

Infrared & Raman spectroscopy of polymers

Structure of polymers

Polymer fracture

Process monitoring of polymer composites

Fasolka, Michael J.

mfasolka@nist.gov

Combinatorial methods and measurements

Nanopatterned substrates

Nanohybrid structures

Surface energy patterning and control

Surfaces and 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+

stan.frukhtbeyn@nist.gov

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

Guttman, Charles M.

charles.guttman@nist.gov

Solution properties of polymers

Size exclusion chromatography

Mass spectrometry 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

Harrison, Christopher

christopher.harrison@nist.gov

Combinatorial methods

Mechanical properties

Polymer thin film properties

Modulus measurements

Hedden, Ronald

ronald.hedden@nist.gov

Siloxane polymers: synthesis and properties

Nanoporous thin films

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

Hudson, Steven D.

steven.hudson@nist.gov

Electron microscopy

Polymeric surfactant and interfacial dynamics

Self-assembly and liquid crystals

Nanocomposites

Biomaterials

Hu, Tengjiao

tengjiao.hu@nist.gov

Dynamic light scattering

Small-angle x-ray scattering

Atomic force microscopy
57

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

Kano, Kenji

kkano@nist.gov

Dielectric relaxation of polymers

Nonlinear dielectric and conductive spectroscopy

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

Kharchenko, Semen

semen.kharchenko@nist.gov

Stress optical properties

Birefringence

Viscoelastic Properties

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

Polymer films and interfaces

Near-edge x-ray absorption fine structure

X-ray and neutron reflectivity

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
58

Research Staff

Lin, Eric K.

eric.lin@nist.gov

Polymer thin films and interfaces

Polymeric photoresists for lithography

Small angle neutron scattering

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

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

McGuiggan, Patricia

patricia.mcguiggan@nist.gov

Atomic force microscopy

Viscoelastic properties

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

Impedence spectroscopy

Dielectric characterization of composites

Photolithography

Nanocomposites

Obrzut, Jan

jan.obrzut@nist.gov

Dielectric relaxation spectroscopy

Electronic properties of polymers and composites

Electronic packaging

Microwave and optical waveguides

Photoelectron spectroscopy (x-ray and UV)

Reliability, stress testing

Parry, Edward E.*

edward.parry@nist.gov

Dental appliance and crown and bridges

 fabrication

Machine shop applications
59

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

Prabhu, Vivek M.

vmprabhu@nist.gov

Small-angle neutron scattering

Polyelectrolytes

Light scattering

Polymer thin films

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. +

schultheiszc@ntsb.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

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

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

Nanocomposite properties

Soles, Christopher

csoles@nist.gov

Polymer dynamics

Inelastic neutron scattering

Low-k dielectric thin films

X-ray and neutron reflectivity techniques

Polymer thin films and lithography

Ion beam scattering techniques

Research Staff
60

Research Staff

Son, Younggon +

Younggon.son@nist.gov

Polymer processing

Polymer phase behavior

Interfacial phenomena

Song, Rui +

rsong@nist.gov

Combinatorial methods and measurements

Polymer debonding

Polymer adhesion and failure

Polymeric peel tests

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

Wallace, William E.

william.wallace@nist.gov

Surface and interface behavior

Electron spectroscopy

Mass spectrometry

Wang, Chia-Ying

cywang@nist.gov

Small-angle x-ray scattering

Polymer diffusion

Microphase transitions of block copolymers

Fluorescence spectroscopy of polymers

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
61

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, Hockin*

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

Research Staff
62
63

Organizational Charts

Organizational Charts

Materials Science and Engineering Laboratory

Polymers

E.J. Amis, Chief

C.R. Snyder, Deputy

Metallurgy

C.A. Handwerker, Chief

F.W. Gayle, Deputy

Ceramics

G.G. Long, Chief (Acting)

(Vacant), Deputy

Materials Reliability

F.R. Fickett, Chief

T.A. Siewert, Deputy

NIST Center for

Neutron Research

J.M. Rowe, Director

Director

Deputy Director

National Institute of Standards and Technology

Director

Boulder Laboratories

Baldrige National Quality

Program

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

L.E. Smith, Director

S.W. Freiman, Deputy Director
64

Eric Amis, Division Chief

Chad Snyder, Deputy Chief

Dawn Bradley, Division Secretary

Karen Hollingsworth, Secretary

Polymers Division (854.00)

Characterization &

Measurement (854.01)

Chad Snyder, Group Leader

Bronny Webb, Secretary

Method Development

Wen-li Wu

Internal Capabilities

Chad Snyder

J. Dunkers

R. Hedden

R. Jones

F. Landis

M. Chiang

M.Cicerone

A. DeReggi

J. Douglas

S. Hudson

Standards & Data

Bruno Fanconi

M. Byrd

W. Blair

K. Flynn

C. Guttman

J. Tesk

J. Lenhart

S. Lin–Gibson

V. Prabhu

F. Starr

W. Wallace

J. Maurey

A. Weaver

S. Wetzel

J. Girard

F. Khoury

D. Liu

W. McDonough

D. Vanderhart

H. Duan

O. Anopchenko

H. Lee

N. Noda

W. Sakai

B. Bauer

C. Chiang

E. Lin

J. Obrzut

C. Soles

J. Antonucci

S.B. Kennedy

C. Simon

F. Wang

N. Washburn

M. Weir

C. Khatri

N. Richards

L. Bailey

E. Hobbie

G. Holmes

F. Phelan

C. Schultheisz

E. Feresenbet

J. He

H. Kim

G. Matsuba

C. Moon

G. Schmidt

K. Shimizu

H. Wang

Z. Wang

Electronics Materials

(854.02)

Wen-li Wu, Group Leader

Bronny Webb, Secretary

Biomaterials

(854.03)

Eric Amis, Acting Group Leader

Barbara Faverty, Secretary

Multiphase Materials

(854.04)

Charles Han, NIST Fellow

Barbara Faverty, Secretary

A. Bur

P. McGuiggan

S. Roth

S. Kharchenko

J. Pathak

Y. Son

K. Beers

A. Crosby

C. Davis

M. Fasolka

S.L. Kennedy

K. Ashley

A. Sehgal

C. Harrison

A. Smith

R. Song

C. Stafford

K. Yurekli

Processing

Characterization (854.05)

Kalman Migler, Group Leader

Trish Snoots, Secretary

Multivariant Measurement

Methods (854.06)

Alamgir Karim, Group Leader

Trish Snoots, Secretary

Organizational Charts