NBS

PUBLICATIONS

A 11 IDO ^5302

NBSIR 81-2424

Characterization of Organometallic

Polymers by Chromatographic

Methods and Nuclear Magnetic

Resonance

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Materials Science

Materials Chemistry Division

Washington, DC 20234

December 1 981

. 1)56

31-2424

1931

,C,t K2 , Naval Ship R & D Center

Annapolis Laboratory

Annapolis. MD 21402

NBSIR 81-2424

5> & & CHARACTERIZATION OF ORGANOMETALLIC

POLYMERS BY CHROMATOGRAPHIC

METHODS AND NUCLEAR MAGNETIC

RESONANCE

MATiOMAL m&lV

Of 0TANDAJEO8 LIBRARY JAN 2 5 1982

Hb-t Ct-CC ' dire

Otioo

y\o

.

fit/

C, ~r

E. J. Parks, R. B. Johannesen, and F. E. Brinckman

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Materials Science

Materials Chemistry Division

Washington, DC 20234

December 1 981

DISTRIBUTION OF THIS DOCUMENT IS UNLIMITED

Prepared for Naval Ship R & D Center

Annapolis Laboratory

Annapolis, MD 21402

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
tw&* u*me&n

t*- OT § $ ?1A;
CHARACTERIZATION OF ORGANOMETALLIC POLYMERS BY CHROMATOGRAPHIC

METHODS AND NUCLEAR MAGNETIC RESONANCE

E. J. Parks, R. B. Johannesen, and F. E. Brinckman

Chemical Stability and Corrosion Division

National Bureau of Standards

Washington, D.C. 20234

Abstract

Organometal 1 ic polymers (OMP) are an increasingly important class of

marine surface anti fouling agents undergoing intensive development by the U.S.

Navy. Commercial procurement of such polymers, expected in the near future,

will require Mil Specs designed to assure reproducibility between batches in

order to achieve satisfactory reliability in service. New analytical methods

are needed in writing such Mil Specs. Candidate OMP's have been characterized

at NBS by size exclusion chromatography (SEC) coupled with tin-specific graphite

furnace atomic absorption spectroscopy (GFAA) as well as by Fourier transform

nuclear magnetic resonance (FT-NMR). The key molecular parameters of many

OMP's, the kinetics of formation of a typical copolymer, and the effects of

different concentrations of free radical initiators on the formation of a

copolymer in a well-stirred reaction system have all been characterized by

119 means of SEC-GFAA chromatograms. FT-NMR spectra of Sn have given kinetic

information in good agreement with that obtained by SEC-GFAA. Both chemical

shift and linewidth of the tin NMR signal have been shown to have an unusually

large solvent and temperature dependence. Directions for future research on

OMP's are discussed.
Key words: Atomic absorption spectroscopy; biocide; chromatography; copolymers

kinetics; NMR; organometal 1 ic polymers; polymers; size exclusion

chromatography; slow-release anti foul ant; tin.

OFFICIAL CONTRIBUTION OF THE NATIONAL BUREAU OF STANDARDS,

NOT SUBJECT TO COPYRIGHT IN THE UNITED STATES
1. Background

Organometal 1 ic polymers (OMP's) prepared from esters of methacrylic acid

and triorganotin methacrylate provide a linear chain molecule incorporating

pendant biocidal organotin moieties [1]. Coated on ship hulls, polymers prepared

from methylmethacrylate (MMA) and tri butyl tinmethacryl ate (TBTM) provide years of

antifouling protection in the marine service environment [2]. The long-term

reliability of organoti n-contai ni ng coatings in service can only be assured if

there is adequate reproducibility of the coating materials from lot to lot.

"Reproducibility" in this context means much more than the usual analytical

measurements such as viscosity, percent tin, etc. The assurance of adequate

quality control may demand, in the final Mil Spec, requirements for average

molecular weight (Mw

or M

n ); molecular weight distribution, MWD; maximum

allowable concentration of low MW tin-containing polymer and/or monomer; and

possibly other less conventional measures of polymer properties as well. The

copolymer composition equation [3] (Eq. 1), is a logical starting point.

According to this equation, the initial concentration of two reacting monomers,

A and B, and their relative reactivity ratios, r

^ and r^, determine the ratio

of components in the copolymer, given ideal behavior:

dA [A]

r l[A]/[B] + 1

dB [B] [A]/[B] + r

2 (1)

Ghanem et al . [4] determined, from empirical Fineman-Ross slopes [5]

based on the composition of copolymers prepared with TBTM and MMA in different

ratios, that the reactivity of TBTM compared to MMA is 0.79 to 1.00 and that

the reaction did exhibit almost ideal behavior. Their copolymers were prepared

in sealed tubes at 60.1 °C with azobi si sobutryoni tri 1 e (ABIN) (0.2 percent by

weight) as initiator.

1
The synthesis of organometal 1 ic polymers is usually performed under very

different conditions in organic solvents [1,6], with stirring. Assuming that

Ghanem's reactivity ratios remain constant under dissimilar reaction conditions,

ideally one could simply continue the polymerization of preselected concentrations of the monomers until all monomeric material became fully incorporated

into a polymer possessing the desired ratio of TBTM and MMA. For optimal

performance, the polymer would exhibit a narrow molecular weight dispersion

(MWD) and a molecular weight (MW) probably in the range of 100,000 daltons

[6], with little or no remaining TBTM or MMA and without substantial homopolymerization of either species.

Apart from the difficulties imposed by different reaction conditions,

several side reactions probably complicate the applicability of Eq. (1) to

real systems. Homopolymerization of TBTM, evident in chromatographic data

earlier reported by us [7] and/or homopolymerization of MMA would alter the

ratio of the end groups that are susceptible to free radical activation and

addition, altering [A] and [B] in the composition Eq. (1), and hence the

composition of the resultant copolymer. This would, at worst, result in

significant bimodal polymerization. Reaction of TBTM or MMA may be complicated

by side reactions depleting one or the other monomer, e.g.

,

hydrolytic fragmentation of TBTM or oxidation of MMA. Reaction of PMMA or of MMA with oxygen

results in low MW peroxides, formal dehdye , and methyl pyruvate [8]. To our

knowledge, no data currently indicate that TBTM or the copolymer is similarly

oxidized. Inhibitors are available to retard oxidation of the copolymer.

It is not asserted here that all of these complications actually occur

during the formulation of an organometal 1 ic copolymer, but rather that a

practical method or methods for characterizing the copolymer and/or the copolymerization process is a prerequisite for understanding and controlling the

rates of addition of different monomers comprising the copolymer.

2
Jewett et al., for example [9], determined that tributyltin cations leach

into water from organotin polymer paints. Initial rapid leaching is followed

by the slower zero order mechanism observed by others [1]. The chemical and

physical processes of coating decomposition have not been conclusively demonstrated. Possibly the slow release mechanism is a result of continuing hydrolytic scission of polymeric ester groups with migration of the freed tributyltin

moieties to the polymer surface, but the initial rapid losses suggest a different

process. Alternately or concurrently, the polymer coating may be slowly

decomposed in service, constantly generating fresh surface by a self-polishing

mechanism [10]. Reliability in long-term service probably requires a uniform

mechanism of decomposition along linear polymer chains of a homogeneous polymer

formulation. However, tin-specific chromatographic analysis of many OMP formulations invariably revealed low molecular weight, tin-bearing species [11]. This

is undesirable from the viewpoint of controlling the release rate of toxic moieties.

Long chain polymers are less mobile and less soluble than materials of the same

composition but of low molecular weight. Thus, in addition to plasticizing effects,

the more facile migration of low molecular weight species, e.g., TBTM monomers,

introduces the risk of complicating mechanisms of release compared to a homogeneous

formulation consisting only of long chain polymers.

For all of these reasons, a valid prediction of the performance of an OMP

and its consequent environmental impact requires, at least, that knowledge of

the manner in which it is formed must be obtained by methods permitting detailed

molecular characterization. This detailed molecular characterization is essential

to ensure reproducibility of the polymer between batches and its consequent

reliability in use. The present report describes NBS research on the

molecular characterization of current candidate OMP's and their polymerization

process by chromatographic methods and nuclear magnetic resonance.

3
2. Experimental*

In two sets of experiments reported below, the conditions of sample

preparation are varied: (1) a kinetic run, in which a mixture of TBTM and

MMA, undergoing polymerization for a total period of 24 h, was sampled at

predetermined intervals to provide partially reacted samples without interrupting the reaction process; and (2) a series of experiments in which copolymerization conditions were varied with respect to the concentration and the

type of initiator added prior to copolymerization.

2. 1 Chemi cal

s

THF (Eastman-Kodak, Rochester, New York) was used throughout the

chromatographic experiments as both solvent and eluent. The THF was purified

by filtration before use (0.5 pm pore size filter) and degassed daily by

magnetic stirring under a vacuum at ambient temperature. Reagent grade benzene

was used as the copolymerization medium. Initiators (benzoyl peroxide and

azobi si sobutyroni tri 1 e) were of the highest available commercial grade.

Standard samples of polystyrene and a sample of polymethylmethacrylate) are listed with their sources in table 1.

Deuterochl oroform of stated isotopic purity 99.8 percent was obtained

from Stohler Isotope Chemicals (Waltham, Massachusetts). Perdeuterobenzene of

stated isotope purity 99.5 percent was obtained from Wilmad Glass Company

(Buena, New Jersey). Tetramethyl ti n of stated purity 99.5 percent was obtained

from Alfa Division, Ventron Corp. , (Danvers, Massachusetts). All were used

without further purification.

*Certain suppliers of chemicals and equipment are identified by name in order to

specify the experimental conditions adequately. This does not imply endorsement

or recommendation by the National Bureau of Standards nor does it imply that the

particular brands of chemicals and equipment named are necessarily the best for

the purpose.

4
Table 1

Standards for Column Calibration

Compound Source

Nomi nal

MW Value M

b

n

Analytical Data

M

C w

MWD

d

Polystyrene 0Arro 600 600 + 7%

__f 1.10

Polystyrene Arro 800 811 + 7% — —

Polystyrene Arro 2,100 2,115 + 7% -- 1.10

Polystyrene Arro 4,0009 3,110 ± 5% — —

Polystyrene Arro 12,000 12,000 12,200 1.10

Polystyrene Arro 19,000 18,900 19,400 1.03

Polystyrene Arro 50,000 50,400 52,100 1.03

Polystyrene Arro 111,000 111,000 111,000 1.00

Polystyrene Arro 233,000 217,000 + 6% 257,000 ± 6% 1.17

Polystyrene Arro 390,000 383,000 392,000 1.02

Polystyrene Arro 630,000 632,000 694,000 1.10

Polystyrene Arro 1,500,000 -- 1,500,000 1.10

Polymethyl Po1y

h methacryl ate sci

.

75,000 " 1.10

a All data provided by manufacturer

Number average molecular weight

QWeight average molecular weight

^Molecular weight dispersion (Mw

/M

n

) e Arro Labs., Joliet, Illinois

^A blank line indicates data not provided

S In preparing the calibration curve, our best estimate value of 3100 was substituted for the manufacturer's nominal WM of 4000

^Polysciences , Inc., Warrington, Pennsylvania

5
2.2 Instrumental Methods

The HPLC-UV/RI-GFAA system [11] is outlined schematically in figure 1.

A high pressure pump (Altex Model 110A, Berkeley, California), equipped with a

single sapphire piston in conjunction with precision inlet and outlet valves,

was used to deliver solvent at the controlled flow rate of 1 mL min ^ in the

present work. Isocratic conditions were employed. Solutions of organometall ic

compounds, or polymers of standard MW, were injected (50 pL) into the SEC

system via an on-line high pressure syringe loading sample injector (Rheodyne

Model 7120, Berkeley, California). An in-line precolumn filter, pore size

2 pm (No. 84560, Waters Associates, Milford, Massachusetts) was used to protect

columns employed for SEC. The columns were packed with porous, highly crosslinked polystyrene-di vinylbenzene (PS-DVB) copolymer (pStyragel , Waters Associates),

have a particle size of 10 pm. Columns used for separations were three pStyragel

3

° columns in series, nominal pore size 10 A. The pStyragel column dimensions

were 300 by 7.8 mm i.d. Columns were connected by 100 mm lengths of 1.5 mm o.d. ,

0.2 mm i.d. stainless steel tubing, and to a fixed wavelength (A = 254 nm)

RI/UV dual detector (Knauer, Utopia Instruments, Inc., Joliet, Illinois).

Columns were maintained at room temperature (22 °C). Medium-walled PTFE

tubing (1.6 mm o.d., 0.7 mm i.d.) transported effluent from the detector cell

outlet to a specially constructed PTFE "well sampler" described previously

[12], from which 20 pL aliquots were automatically withdrawn at 55.5 s intervals

(At). A Perkin-Elmer (Norwalk, Connecticut) Model 360 dual-beam atomic absorption

spectrophotometer with deuterium lamp background corrector and Model HGA 2100

graphite furnace atomizer (GFAA) were used for specific element detection.

GFAA program: A, 224.6 nm; drying time, 10 s, 100 °C; charring time, 10 s,

200 °C; atomization time, 10 s, 2700 °C; atomization interval, 55.5 s. In

6
UV-RI Detector 7

Figure

1.

Block

diagram

summarizing

the

SEOUV/RI-GFAA

system,

including

accessory

devices.

In

the

present

experiments,

the

auto

sampler

continuously

aliquoted

20

pL

specimens

into

the

graphite

furnace

at

intervals

of

55.5 s

[11].
GFAA chromatograms, the observed peak heights represent measured absorbances

due to the quantities of an element contained in a 20 pL aliquot introduced

into the furnace and volatilized at 2700 °C. Only about 2 percent of the

total effluent is volatilized at a flow rate of one mL min \ An automatic

digital integrator (Infotronics Model CRS-204, Infotronics Corp. , Austin,

Texas) was used to obtain a digital record of AA absorption intensities.

A Waters Model R401 differential refractive index indicator was used

to obtain the ARI data from which was prepared the histogram of 0MP-1, shown in

figure 2. The sample was dissolved (1/100 w/v) in THF and injected (300 pL) into

a system consisting of four SEC columns in series: two pStyragel columns

3

° having nominal pore size of 10 A, and two pStyragel columns having nominal pore

2 ° size of 10 A. The column dimensions, the connectors, and flow rate were as

described above.

Eluent was collected during this entire chromatographic run in either

0.5 mL or 1.0 mL segments for subsequent off-line analysis for tin by GFAA, in

order to plot the intensities of GFAA tin signals obtained from 20 pL aliquots

of the consecutive fractions and compare their intensities with those of corresponding ARI signals.

SEC column calibration was performed with polystyrene standards, having

a molecular weight range encompassing that of observed 0MP fractions. A calibration curve is illustrated in figure 3 and is presented on the scale of elution

volume (V^) in figure 4.

8
OMP-1

Sn Content

105 104 10

3 102 MW

Figure 2. SEC-RI-GFAA chromatogram of OMP-1, a terpolymer

of methyl methacrylate, tributyltin methacrylate,

and tripropyltin methacrylate. Solvent, THF.

Columns: Waters pStyragel (four) in series; two

O of average pore size 10 3 A and two of average pore

O size 10 2 A. Mobile phase, THF . Flow rate,

1.0 mL min-1

. RI detector, Waters Model R-401.

Injected volume, 300 pL. Injected concentration

of polymer, 3.0 mg/300pL. Fractions were collected

for off-line determination of tin by tin-specific

GFAA. Each peak in the respective histograms

represents a percentage of the total amount of

detected tin (GFAA) or detected materials (ARI).

9

Total

Material,

%
COLUMN CALIBRATION

/

Figure 3. Column calibration based on elution volumes of PS and

toluene. Each point represents the intersection of tangents

extrapolated from straight line portions of the respective

chromatographic absorption spectra of polystyrene standards

listed in table 1. V^' represents retention volume corrected

for 0.1 mL of dead volume between the column and the UV/RI

detector. The point for PMMA (open oval) was omitted in

calculating slope and correlation coefficient (0.997) of

the plot of log MW vs V p

'.

10
1 r- 1 ,

1 20 40

V b. mis

Figure 4. SEC-RI-GFAA chromatograms of TBTM-MMA copolymers reacted

for 24 h in refluxing benzene (80.1 °C) in the presence

of concentrations of benzoyl peroxide incremented in

logarithmic steps.

2.2.1 Nuclear Magnetic Resonance

All NMR spectra were run on a CXP-200 NMR spectrometer (Bruker

Instruments Inc., Billerica, Massachusetts), equipped with a tunable broad band

probe, at a field strength of 4.7 T. All spectra were run in 20 mm o.d. spinning

sample tubes. Tin-119 spectra (74.6 MHz) were run on a 10 percent w/v solution

of polymer in THF. The spectral width was typically 36 ppm using a 35 ps pulse

11
(90° flip angle). The number of data points was 8192 (8 K) , and a 6 Hz line

broadening function was used before Fourier transformation. Since preliminary

experiments showed the field drift to be negligible compared to the width of

the Sn lines, the spectrometer was run unlocked. Decoupled spectra were run

in the nOe suppressed mode. Maximum acquisition time was not over 20 min. All

chemical shifts are reported with reference to external (CHg)^Sn as zero, with

shifts to high frequency (downfield) of the resonance reported as positive [13].

Carbon-13 spectra (50.3 MHz) of polymer were run on a 20 percent w/v solution

in benzene containing about 10 percent benzene-d^. TBT0 was run as a neat

liquid containing five percent (CD^^CO as a lock. The spectral width was

chosen according to the spectral region (aliphatic, carbonyl, or total) that

was to be viewed. A tailored pulse sequence was used to minimize the

interference from the high concentration of benzene [14]. The number of data

points taken was either 8 K or 4 K, with zero fill, if needed, to improve

interpolation on peaks. Line broadening was used according to the particular

signal it was desired to emphasize. The spectrometer was locked to the deuterium

signal of the benzene-dr

. All spectra were run with proton decoupling, using

b

the two level sequence to preserve nOe with minimum sample heating. Acquisition

time varied from less than one hour for the aliphatic region to overnight (14

h) for the carbonyl region. All chemical shifts are reported with respect to

benzene taken as 128.0 ppm.

2. 3 Experiments

In this section we describe first kinetic studies of copolymerization,

then the results of a series of copolymerizations conducted under varied

conditions, and finally the treatment of data obtained from the experiments.

12
2.3.1 Kinetic Runs

For the kinetic runs, TBTM was commercially prepared from

high-purity bis(tributyl tin) oxide (TBTO) and methacrylic acid. The monomer was

recrystallized from petroleum ether at -15 °C to obtain a product claimed by the

manufacturer to be typically 98 percent pure after recrystallization. Decomposition of this product was inhibited by addition of 100 ppm of p-methoxyphenol

.

The product was stored at 4 °C until used. Methyl methacrylate, commercially

prepared and inhibited with 25 ppm of p-hydroqui none was used as received. With

benzene as the copolymerization medium, a sol vent-to-polymer ratio of 2:1 by

weight was determined to be optimum. Commercial benzoyl peroxide (1 percent

by weight based on the sum of TBTM and MMA) was employed as the initiator. The

tetrahydrofuran (THF) used as the solvent for aliquots of sample, contained

butyl ated hydroxytol uene preservative and was purified by filtration before use,

employing an organic clarification kit equipped with filters of 0.5 pm pore size.

TBTM (348.8 g, 0.93 mol) and MMA (80 g, 0.8 mol) were added

to 857.6 g of benzene in a 2-L, three-neck flask equipped with a thermometer,

septum, and condenser. To this mixture was added 4.29 g (0.018 mol) of benzoyl

peroxide. The flask and contents were warmed on a heating mantle controlled

by a variable transformer at the reflux temperature of benzene (80.1 °C) with

continuous magnetic stirring. Ten-mL aliquots were taken from the reaction

mixture after preselected periods of reaction (table 2) and diluted immediately

to 100 mL with cold THF. The final aliquot in the kinetic series was taken

after a 24 h reaction time. These samples were examined by chromatography [11]

and by

119

Sn FT-NMR.

13
Table 2

Fractionation by SEC of Aliquots Taken During Copolymerization of TBTM

and MMA , with GFAA 1Detection of Tin- Containing Moieties

A1 i quot

Number

Time of

React i on

,

min.

Fracti on Integrati on mV

C

A

a Counts

% Sn

Fraction

Integration

mV

C

B

b

Counts

% Sn

1 o d

19,670 21.1 73,540 78.9

2 o e 19,430 17.8 89,730 82.2

3 30 53,240 40.1 79,660 59.9

34,490 41.3 48,990 58.7

4 60 43,070 53.2 37,900 46.8

5 180 142,000 59.2 97,810 40.8

65,000 58.0 47,050 42.0

6 360 120,420 64.1 67,510 35.9

7 726 123,840 61.1 78,950 38.9

8 1440 94,850 67.3 46,030 32.7

9 AFTER

f

145,620 86.5 22,700 13.5

a Fraction A = MW 200,000-1,000 daltons

^Fraction B = MW 500-100 daltons

c Summation of counts

d

0 = Aliquot taken prior to heating

e 0 = Aliquot taken at the time at which refluxing began

^Aliquot taken after replacement of refluxing benzene by refluxing Stoddard

solvent, involving increase in temperature to 120 °C

14
2.3.2 Varied Conditions of Polymerization

2. 3. 2.1 Samples Initiated by Varied Concentrations of

Benzoyl Peroxide

To determine the effect on polymer properties of

increasing concentrations of benzoyl peroxide initiator, mixtures were prepared

of TBTM (375.5 g, 1 mol) and MMA (100 g, 1 mol) to 950.1 g of benzene. The

concentrations of benzoyl peroxide were 0.03 percent (0.141 g, 0.0006 mol),

0.10 percent (0.470 g, 0.002 mol), 0.30 percent (1.410 g, 0.006 mol), and

1.0 percent (4.700 g, 0.0197 mol). The respective batches were subjected to

reaction for 24 h. Aliquots of these samples were diluted with THF (10 midi luted to 100 mL) at 4 °C and then stored at the temperature of dry ice

(-80 °C), pending chromatographic analysis by size exclusion chromatography

coupled with ultraviolet and graphite furnace atomic absorption spectroscopy

detectors (SEC-UV-GFAA)

.

2. 3. 2. 2 Samples Initated by ABIN

In addition to samples initiated by benzoyl

peroxide, two other samples were prepared at 60 °C with the same proportions of

TBTM, MMA, and benzene, but including, respectively, 0.03 percent and 0.10 percent

(0.001 mol and 0.0029 mol) of azobi si sobutyroni tri 1 e (ABIN). An attempt to

prepare a sample initiated by 1.0 percent (0.029 mol) of ABIN resulted in

eruption of the contents of the flask within minutes, possibly as a result of

the rapid decomposition of initiator into a large volume of nitrogen gas and

free radicals in a viscous solution. A powdery white solid found in the hood

surrounding the reaction flask was assumed to be a copolymer formed almost

instantly under the reaction conditions. Because results obtained when using

lower molar quantities of ABIN were similar to those using the same amount of

benzoyl peroxide, an experiment with 0.3 percent of ABIN was omitted.

15
2. 3. 2. 3 Extended Time of Reaction at a Lower Temperature

A sample of TBTM-MMA copolymer was prepared in

the presence of 1.0 percent of benzoyl peroxide at a controlled temperature of

63.3 °C rather than 80 °C, for a period of time extended to 72 h, in order to

estimate the effect of the slower decomposition of the initiator into free

radi cal s.

2. 3. 2. 4 Addition of Benzoyl Peroxide in Consecutive

Increments

A sample of TBTM and MMA was copolymerized at

80.1 °C in the presence of 0.30 percent increments of benzoyl peroxide added

initially, after 24 h, and after 48 h. After 24 h, 48 h, and 72 h, 10 mL

aliquots were diluted with cold THF to 100 mL and stored at dry ice temperature

pending chromatographic analysis.

2. 3. 2. 5 0MP-1 Polymer

A sample of 0MP-1, the terpolymer product of tripropyl tin methacrylate, methyl methacrylate, and tri butyl tin methacrylate

was obtained in approximately 1:1 solution in Stoddard solvent (mineral spirits).

The sample was dissolved in THF to provide a solution containing about 1 percent

of polymer (w/v) and was examined by chromatographic analysis using a differential

refractive index (ARI) detector. Collected eluent fractions were subsequently

analyzed for tin by off-line atomic absorption spectroscopy.

2. 3. 2. 6 0MP-S

0MP-S, a copolymer of TBTM and MMA , was obtained

in a solution of benzene. This was subjected in benzene (final composition

20/100 w/v) to characterization by ^C FT-NMR, for comparison with the

13

C FT-NMR

spectrum of TBT0 as a model compound.

16
2.3.3 Methods of Data Reduction

Weight average and number average molecular weights (M^ and

M

n

) were determined from chromatographic GFAA peaks corresponding to individual

polymeric fractions by the methods described in detail by Yau, Kirkland, and

Bly [15,16]. The intensities of individual tin peaks (h.), proportional to

experimental peak heights, were obtained from the digital integrator record.

Molecular weights (M.) corresponding to each (h.) value were obtained by

comparing the corrected elution volume (Vp‘) with a corresponding point on the

column calibration curve shown in figure 4. The logarithm of the molecular

weight of the tin-containing species is assumed for present purposes to be that

of the polystyrene standard sample that elutes with a corresponding elution

volume. From the (h.) and (M.) values, M^, M , and molecular weight dispersions

(MWD) are calculated according to the following relationships [15]:

M = w 22

<h

i'

M

i

i = 1

n r-,

( 2 )

i = 1

M =

n 2>> i = 1 n X. (h

i /Mi

(3)

i = 1

M

MWD = rp

M

n (4)

The area of each polymer peak was accurately calculated by

summation of the individual tin peaks [12,17,18], GFAA chromatograms usually

were separated into fractions at a Vp' of 30 mL, corresponding to a species

17
having a molecular weight of about 500. In certain cases, there appeared to be

peak overlap, involving not more than one individual tin signal of relatively

low intensity, shared by two polymeric fractions. In these cases, 50 percent

of the tin signal was attributed to each fraction in summing up total peak

areas.

The percent of tin in each separated fraction was obtained

by summing up the total of GFAA tin signals, dividing that quantity into the

sum of tin associated with the polymer fraction, then multiplying by 100.

3. Results and Discussion

3. 1 Chromatographic Methods of Analysis

The system shown schematically in figure 1 has been adapted from several

experiments conducted in NBS laboratories [7,11,18] for fractionation of OMP formulations with multiple detection on-line. For optimal column performance, overloading must be avoided [18], and the sensitivity of GFAA detection to nanogram

quantitation of molecular tin species [12,19] is admirably suited to problems

requiring analysis in trace amounts of numerous individual polymer formulations

fractionated by SEC.

One example is the kinetic analysis of TBTM-MMA copolymerization

under carefully controlled conditions [7]. Since TBTM is eluted by a volume of

eluent THF corresponding to that of the late eluting fraction of typical OMP

formulations [11] (figures 5 and 6), fractionation by size demonstrated conversion of the tin-bearing moiety with time of reaction. As shown in figure 7 [7],

the chromatographic data of a 24 h kinetic run fit a pseudo first-order equation

with a reasonably high coefficient of correlation when the degree of conversion

is compared with the logarithm of reaction time. Equally important, we found

no evidence of discontinuity in this rate of conversion over the period of

18
SEC-UV-GFAA CHROMATOGRAMS OF TBTM

UV

A A

m L

40

Figure 5. SEC-UV-GFAA chromatogram of tributyl tin methacrylate

purified by recrystallization from petroleum ether.

Solvent, THF. Columns: Waters pStyragel (three)

in series; average pore size 103 A, mobile phase,

THF. Flow rate, 1.0 mL min'"1

. UV detector: Knauer

UV/RI Dual Detektor, operating in the UV mode at

254 nm. UV sensitivity, 0.003 AUFS. Injected

volume, 50 pL. Injected concentration of TBTM,

50 pg/50pL. GFAA detector, Perkin-Elmer 360.

19
OMP -S

i i i i r

0 10 20 30 40

Figure 6. SEC-UV-GFAA chromatogram of a copolymer of TBTM and

MMA. Solvent, THF. Columns: Water pStyragel (three)

in series; average pore size 103 A, mobile phase, THF.

Flow rate, 1.0 mL min -1

. UV detector: Knauer UV/RI

Dual Detektor, operating in the UV mode at 254 nm. UV sensitivity, 0.003 AUFS. Injected volume, 50 pL.

Injected concentration of OMP-S, 25 pg/50 pL.

20
Conversion of T BTM to Copolymer

Figure 7. Increases in high polymer fraction (Ap) plotted as a function of natural logarithm of reaction time (In t) in

minutes, during the free radical copolymerization of TBTM

and MMA at 80.1 °C. The observed points fit the equation,

Ap = k Ain t + b, with a linear regression coefficient,

r = 0.978, s = 0.036 (7).

reaction time; total conversion, however, of the undesired TBTM fraction

would have required a period of reaction of about 30 days, assuming continuity

of the conversion process for that period of time.

The molecular weight and the molecular weight dispersion (or

narrowness) of the high polymer fraction are important polymer parameters, as

21
well, and were shown to be essentially independent of the extent of conversion.

These facts indicate that polymer chain growth was much more rapid than initiation.

Thus, a small number of chains rapidly attained their maximum growth to a

molecular weight of about 50,000 daltons. Moreover, as mentioned, molecular

size did not exceed 50,000 daltons, even after prolonged reactions, suggesting

that mobility, or another physical parameter related to molecular size, determined chain growth and termination in a medium of competitive free radical

reactions.

Varying the concentration of benzoyl peroxide initiator resulted,

after 24 h of reaction, in the formulations whose chromatograms are exhibited

in figure 4. The pertinent data are summarized in table 3.

The MW of the sample initiated with a one percent concentration of

benzoyl peroxide is much lower than that of the 24 h aliquot of the kinetic

series. Initiator concentrations, monomer concentrations, and chain transfer

Table 3

Effect of Initiator Concentration (Benzoyl Peroxide) on Molecular

Characteristics of TBTM-MMA Copolymer

[I]

c

1 n [ I ] Conversion MWD

a M

b w

(daltons) (%)

c (%)

0.03 -3.506 60.0 1.44 34,600

0.10 -2.303 71.0 2.11 30,800

0.30 -1.204 77.0 2.58 22,300

1.00 0.0 84.0 3.81 15,500

d

r 0.991 0.981 -0.988

aMWD = M /M

b w n Mw

= weight average mol weight. See Experimental.

Q [I] = percent initiator by weight of TBTM and MMA in the reaction mixture

Coefficient of linear correlation between ln[I] and conversion, MWD, and M , respectively

22
agents all affect the MWD of poly (methyl methacryl ate) [20]. From the presumed

dependence of initiator activity on diffusion control [20], we infer that

differences in experimental conditions, such as unequal stirring rates, have

a surprisingly large effect on the formation of TBTM-MMA copolymer and will

require careful control and evaluation in future copolymerization experiments.

The data in table 3, however, do show a striking correlation between the

logarithm of the initiator concentrations and corresponding conversion, dispersion, or molecular weight. These data suggest experimental variations to force

the reaction to a higher conversion than any obtained in the present experiments,

e.g., by incremented increases in stirring rates and/or incremental use of small

amounts of initiator, followed by additional quantities, perhaps much larger,

over an extended period of time. However, incremental addition of a low

concentration (0.03 percent) of benzoyl peroxide under constant conditions

resulted in little change in the degree of conversion after the first 24 h

(table 4).

At 63 °C, benzoyl peroxide dissociates much less rapidly than at 80 °C.

A copolymer initiated by 1.0 percent benzoyl peroxide at 63 °C and allowed to

react for 72 h displayed the properties listed in table 4. The MW is much

higher than that of the copolymer obtained at 80.1 °C (table 3) in the presence

of 1.0 percent benzoyl peroxide but the MWD is nearly the same. The increase

in MW shown by this single experiment, together with the relative insensitivity

of MWD to temperature, suggests that evaluation of the effect of experimental

parameters must include temperature as one of the variables.

It is evident from tables 3 and 4 that azobi si sobutryoni tri 1 e and benzoyl

peroxide initiated reactions yield polymers possessing similar molecular properties, at least for the low concentrations (0.03 and 0.1 percent) of ABIN that

have been examined.

23
Table 4

Copolymeri zati on of TBTM and MMA Under Various Conditions

Initiator [I]

%

Time

(h)

Temp

°C

MW

a (dal tons)

MWD

b Conversion6

%

Benzoyl peroxi de 0.03 24 80.1 24,800 1.84 67.3

Benzoyl peroxi de 0.06

C

48 80.1 22,900 1.53 70.1

Benzoyl peroxi de 0. 09

d

72 80.1 21,300 1.73 66.8

Benxoyl peroxi de 1.0 72 63.3 29,250 4.08 75.8

ABIN 0.03 24 60.0 40,900 1.61 61.8

ABIN 0.10 24 60.0 28,000 2.02 73.8

aWt. average MW

Q Increments of 0.03 percent and 0.03 percent w/w added consecutively at 24 h

i nterval

s

Increments of 0.03, 0.03, and 0.03 percent added consecutively at 24 h intervals

e Conversion based on TBTM with tin-specific detection.

The interpretations discussed so far have all been based on transformations of TBTM only, without recourse to changes in monomeric MMA. The reasons

are that the sensitivity of tin detection by GFAA is particularly favorable for

evaluating conversion of TBTM, and that TBTM includes the important biocidal

moiety that must be incorporated into the polymer, in order for coatings

materials actually to work as biocides.

It is experimentally more difficult to follow MMA conversion. The

structural similarity to TBTM renders difficult any distinction between the

two substances by optical spectroscopy. In figure 2, a GFAA histogram is

superimposed on a ARI chromatogram of a commercially prepared terpolymer. The

low MW peak in the ARI chromatogram could be due to both TBTM and MMA; it

24
is not possible to quantitate the conversion of MMA from this single chromatogram.

The relatively small tin peak in the low MW fraction indicates a degree of TBTM

conversion equal to or greater than the conversion of MMA. A kinetic run

combining SEC-ARI chromatograms with superimposed GFAA histograms has not been

attempted but would provide a great deal of information on the simultaneous

conversion of both tin-bearing and tin-free monomer species.

3.2 FT-NMR

119 Figure 8 represents the Sn FT-NMR spectra of samples selected from

119 the kinetic run illustrated in figure 7. Figure 9 is the Sn FT-NMR spectrum

of TBTM. Comparison of the two figures demonstrates conclusively that the lower

field peak is due to polymer; this increases in intensity at the expense of the

high-field peak. The chemical shift of the tin signals appeared to show a qualitatively large temperature dependence in uncontrolled experiments. A model system,

consisting of freshly recrystallized TBTM, was chosen for further experiments.

119

The Sn NMR spectrum of TBTM was run at 10° intervals from -20 °C to +10 °C

in CDC1

3

(locked to solvent) and in THF (locked to added five percent C^D^.). The

119

Sn chemical shift in each solution varied linearly with temperature. A summary

of results is given in table 5 and demonstrates that both temperature and solvent

effects are indeed large.

13 Figures 10 and 11 indicate C FT-NMR spectra of tri butyl tin oxide

and of a commercial copolymer prepared from TBTM and MMA. Considerable

differences arise. Carbon-13 signals appearing near 13, 16, 27, and 28 ppm

in the polymer are attributed to the tributyltin residue. There are sharp

lines near 19, 125, 135, and 170 ppm, which are probably due to monomer not

totally reacted. The two broad signals near 180 ppm are attributed to carbonyl

groups in the polymer; one arising from MMA and the other from TBTM. Assignment of these lines to their respective monomers awaits examination of comparison

25
Table 5

119

Sn FT-NMR of TBTM

Solvent 6* at 0 °C A6/At

Linewidth

at 0 °C ALW/At

ppm ppm/°C Hz Hz/°C

CDC1

3

110.90 -0.0781 9 0.0

THF 65.25 +0.4748 60 -2.04

*(CHg)

4

Sn =0.0 ppm; downfield positive

spectra of PMMA and polymerized TBTM (PTBTM). The interpretation of the methyl

region is complicated by the presence of sharp lines, which are probably (at

least in part) due to monomers. The complexity of the carbonyl region (near

180 ppm) suggests that monomer units are present with all possible nearest

neighbors; i.e., random addition to TBTM or MMA to the end of the growing

chain. Confirmation of these preliminary results will await analysis of PMMA

of known tacticity, as well as PTBTM prepared under conditions that will allow

at least an informed guess as to the tacticity of the product.

The broad tin signal found in THF is characteristic of a system in

which the atom observed (i.e., tin) is present in two or more different bonding

arrangements that are exchanging at a rate comparable with the NMR time scale

4 -1

of approximately 10 s . A very rapid exchange would give a sharp signal at a

weighted average chemical shift; a very slow exchange would give two or more

separately resolved sharp signals. In favorable cases, the kinetics of exchange

can be determined by line-width measurements as a function of temperature. In

the case of the OMP's, the unsuitability of THF and other solvents of similar

119 intermediate coordinating power, as a solvent for Sn NMR measurements, is

amply demonstrated.

26
SN - 119 FT - NMR OF POLYMERIZATION REACTION

Figure 8. 119 Sn [

1 H ] FT-NMR spectra of copolymers of TBTM-MMA, following reaction

for selected periods of time and showing regular increase in area

of signal at lower field, attributed to Sn in polymer. Identical

samples were used to obtain data to fit the kinetic equation

exemplified in figure 7.

27
Si-119 FT-NMR OF TBTM

r

~— i i 1

1—— n— —

i

100 64 28

-*

PPM FROM (CH

3

) 4

Sn

Figure 9. 119 Sn [

1 H ] FT-NMR spectrum of TBTM, demonstrating

attribution of high field absorbance in figure 8

to unreacted TBTM.

28
C-13 FT-NMR OF TBTO

I 1 1 1

1 30 20 10

PPM FROM EXTERNAL IMS

Figure 10. 13 C [

1 H ] FT-NMR spectrum of bi s(tributyl ti n) oxide,

[(CH 3 CH2 CH2 CH2 ) 3 Sn] 2 0

29
C-13 FT-NMR OF A TBTM MMA COPOLYMER

f

1 1 1 1 1 1

220 180 140 100 60 20

PPM FROM EXTERNAL IMS

Figure 11. 13 C [

1 H] FT-NMR spectrum of a copolymer of TBTM

and MMA.

30
Some effort will be spent on finding the most suitable solvent; however, we do

not expect to pursue the measurement of exchange kinetics vigorously as a part

of this program.

Coupling of a

1 H FT-NMR system to an HPLC column has been reported

[21,22,23] as an unusual detector which has advantages over the more commonly

used detection means in certain special cases. The analysis of a polymerizing

mixture of TBTM and MMA may well be one such special case. Proton NMR can

unequivocally measure the decrease in signal from protons on doubly-bonded

carbons as the polymerization proceeds and thus give kinetic information which

does not require pre-calibration of the detector system (inasmuch as proton

signal intensities can easily be made directly proportional to proton numbers).

The Bureau has a 1.4 T (60 MHz) NMR system which has been converted for FT-NMR;

it has been little used since the high field NMR facility was installed and is

available for coupling to an HPLC column. It is not known at present whether

it will be possible to distinguish between the =CH2 signals from MMA and TBTM

at 60 MHz. If this is possible, the additional analytical information it

provides will be of great value. Even if only the total signal from =CH2 can

be measured, these results can be combined with the analyses for Sn performed

by GFAA and the amount of MMA still unreacted can be determined by difference.

Accordingly, the construction of an HPLC-FT-NMR system will be pursued in FY82.

At the present time, sensitivity considerations limit the proposed system to

proton NMR analysis.

3. 3 Limitations of Column Calibration with Polystyrene Standards

The assumption underlying SEC column calibration with standard

samples of known molecular weight is that retention is size dependent, equally

for the standards and unknown whose MW we wish to estimate. This is strictly

true only if stereoel ectronic interactions between the packing and the respective

31
eluents are the same. pStyragel (polystyrene cross-linked with di vinyl benzene)

is not entirely free of surface adsorptivity for polar molecules [24-27] and the

validity of MW data based on comparisons between unknowns and standards perforce

requires essentially constant experimental conditions. Absolute measurements

of MW fractions will require a technique that is directly dependent on size and

not on chromatographic retention of MW standards. Low angle laser light scattering

technology appears to be one approach capable of determining the molecular

weight of chromatographic fractions without recourse to the retention times of

standard solutes [28].

The SEC-UV/RI-GFAA work so far reported [7,11,18] has involved analytical

scale chromatography. Alternatively, fractional precipitation [29] holds promise

for providing the larger quantities of specific polymer fractions required for

119 13 characterization of configurational sequence by Sn FT-NMR and C FT-NMR, and

absolute identification of low MW species. However, this bulk method lacks the

rapidity and convenience of SEC-UV/RI-GFAA for multiple problem solving in

synthesis and characterization of OMP's.

3. 4 Directions of Future Research

Future research must be designed to provide further information required

for writing a Mil Spec which can be met by potential commercial suppliers and

which will assure adequate reliability of organotin polymers in use. Analytical

SEC-UV/RI-GFAA has identified the research in OMP synthesis and characterization

requiring most urgent attention:

3.4.1 Simultaneous determinations of the rates of conversion of the

individual types of monomer in the copolymerization of MMA and TBTM. This

problem appears to be readily amenable to SEC-RI-GFAA characterization of either

an extended kinetic run, such as described already [7], or a series of interrupted runs involving selected monomer compositions [2,3].

32
3.4.2 Development of a chromatographic technique for performing

absolute MW determinations. Because the physico-chemical behavior of standard

samples may not be the same as that of unknown polymers, an absolute method

is desired. A low angle laser light detector [28] provides the most promising

technology available.

1 13 119 3.4.3 Refinement of H, C, and Sn NMR by comparison of experimental spectra with those of known homopolymers in order to measure degree of

polymerization in kinetic runs or configurational sequencing in finished polymers.

3.4.4 Correlation of polymer MW with several selected stirring

rates, carefully controlled.

3.4.5 Synthesis of model copolymers ultimately providing reference

standards for industrial or Mil-spec use.

4. Acknowledgments

We acknowledge with pleasure partial support of the research described

herein by the United States Naval Ship Research and Development Center (USNSRDC,

Annapolis, Maryland) and of prior research, referenced in this paper, by the

Office of Naval Research (ONR, Washington, D.C.). We are grateful for helpful

advice and assistance from Kenneth L. Jewett, William R. Blair, Leslie E. Smith,

Daniel W. Brown, and John Maurey, all of NBS; and from Vincent J. Castelli,

Clarene E. Mull in, and Debbie M. Andersen all of the USNSRDC (Annapolis).

5. References

[1] E. J. Dyckman and J. A. Montemarano, "Anti fouling Organometal ic Polymers:

Environmentally Compatible Materials," Report No. 4186, Naval Ship R&D

Center, Bethesda, MD, 1974. 31 p.

[2] W. L. Yeager and V. J. Castelli, "Antifouling Applications of Various

Tin-Containing Organometal 1 ic Polymers," in Organometal 1 ic Polymers , C. E. Carrahar, Jr., J. E. Sheats, and C. U. Pittman, Jr., Eds., Academic

Press, NY, 1978, pp. 175-180.

33
[3] F. R. Mayo and F. M. Lewis, Copolymerization I. A basis for comparing the

behavior of monomers in copolymerization; the copolymerization of styrene

and methacrylate, J. Am. Chem. Soc. 66, 1594 (1944).

[4] N. A. Ghanem, N. N. Messiha, N. E. Ikaldesus, and A. F. Shaaban, Organotin

polymers. I. Copolymerization parameters of tri butyl tin methacrylate with

methyl methacrylate, propyl methacrylate and butyl methacrylate, Eur. Poly.

J. 15, 823 (1979).

[5] M. Fineman and S. D. Ross, Linear method for determining monomer reactivity

ratios in copolymerization, J. Poly. Sci. 5, 259 (1950).

[6] J. C. Montermoso, T. M. Andrews, and L. P. Marinelli, Polymers of tributyltin

acrylate esters, J. Poly. Sci. 32, 523 (1958).

[7] E. J. Parks, F. E. Brinckman, C. E. Mullin, D. M. Anderson, and

V. J. Castelli, Characterization by tin-specific size exclusion chromatography

of the free radical copolymerization of tributyltin methacrylate and methyl

methacrylate, J. Appl Poly. Sci. 26, 2967 (1981).

[8] A. Ravve, Organic Chemistry of Macromolecules, Marcel Dekker, NY, 1967,

p. 216.

[9] K. L. Jewett, W. R. Blair, and F. E. Brinckman, "New Methods for Speciation

of Organotin Leachates from Anti fouling Paints and Polymers," Sixth Int.

Symp. on Controlled Release of Bioactive Mater., New Orleans, LA.,

August 6-8, 1979, Abstracts, pp. 11-13 to 11-16.

[10] N. A. Ghanem, N. N. Messiha, M. M. Abd El Malik, N. E. Ikaldesus, and

A. F. Shaaban, New terpolymers with pendant organotin moieties as anti fouling

coatings, J. Coatings Tech. 53, 57 (1981).

[11] E. J. Parks and F. E. Brinckman, Characterization of bioactive organotin

polymers: fractionation and determination of MW by SEC-GFAA i_n Controlled

Release of Pesticides and Pharmaceuticals, D. H. Lewis, Ed., Plenum Press,

NY, 1981, pp. 219-238.

[12] F. E. Brinckman, W. R. Blair, K. L. Jewett, and W. P. Iverson, Application

of a liquid chromatograph coupled with a flameless atomic absorption

detector for speciation of trace organometal 1 ic compounds, J. Chromatogr.

Sci. 15, 493 (1977).

1

1

q

[13] P. J. Smith and A. P. Tupciauskas, Chemical Shifts of Sn Nuclei in

Organotin Compounds, Ann. Repts. NMR Spectroscopy 8, 291 (1978).

[14] G. A. Morris and R. Freeman, Selected excitation in Fourier transform

nuclear magnetic resonance, J. Magnetic Res. 29, 433-462 (1978).

[15] W. W. Yau, J. J. Kirkland, and D. D. Bly, Modern Si ze Excl usion Liquid

Chromatography , Practice of Gel_ Permeation and Gel Filtration Chromatography , Wi ley-Interscience, NY, 1979, pp. 4-8.

[16] Reference 15, pp. 318-22.

34
[17] F. E. Brinckman, K. L. Jewett, W. P. Iverson, K. J. Irgolic, K. C. Erhardt,

and R. A. Stockton, Graphite furnace atomic absorption spectrophotometers

as automated element-specific detector for high pressure liquid chromatograph (HPLC), the determination of arsenite, arsenate, methyl arsonic acid,

and dimethylarsinic acid, J. Chromatogr. 191, 31 (1980).

[18] E. J. Parks, F. E. Brinckman, and W. R. Blair, Application of a graphite

furnace atomic absorption detector automatically coupled to a high performance liquid chromatograph for speciation of metal-containing macromolecules,

J. Chromatogr. 185 , 563 (1979).

[19] K. L. Jewett and F. E. Brinckman, Speciation of trace di- and triorganotins

in water by ion-exchange HPLC-GFAA, J. Chromatogr. Sci. 19 (1981), in press.

[20] T. J. R. Weakley, R. J. P. Williams, and J. P. Wilson, The molecular weight

distribution in some poly(methyl methacrylates), J. Chem. Soc. London,

3963 (1960).

[21] N. Watanabi and E. Niki, Direct coupling of FT-NMR to high performance

liquid chromatography, Proc. Japan Acad. 543 , 194 (1979).

[22] E. Bayer, K. Albert, M. Nieder, E. Grom, and T. Keller, On-line coupling

of high performance liquid chromatography and nuclear magnetic resonance,

J. Chromatogr. 186, 497 (1979).

[23] J. F. Haw, T. E. Glass, D. W. Hausler, E. Motel, and H. C. Dorn, Direct

coupling of a liquid chromatograph to a continuous flow hydrogen nuclear

magnetic resonance detector for analysis of petroleum and synthetic fuels,

Anal. Chem. 52, 1135 (1980).

[24] H. J. Mencer and Z. Grubi sic-Gal 1 ot , Influence of solvent polarity on elution

volume in the case of polar polymers, J. Liquid Chromatogr. 2, 649 (1979).

[25] A. Campos and J. E. Figuerelo, Polymer retention in gel permeation chromatography in pure and mixed eluents, Makromol. Chem 178, 3249 (1979).

[26] M. Mimaret, Z. Sir, and J. Coupek, Analysis of esterification mixtures of

terephthalic acid and ethylene glycol by gel chromatography, Die Angewandt.

Makromolekulare Chemie 64, 147 (1977).

[27] M. Popl , J. Fahnzich, and M. Stegskal , Adsorption effect in GPC separation of

polycyclic aromatic hydrocarbons, J. Chromatogr. Sci. 14, 537 (1976).

[28] R. C. Jordan, Size exclusion chromatography with low angle laser light

scattering detection, J. Liquid Chromatogr. 3, 439 (1980).

[29] J. F. Johnson, M. J. R. Cantow, and R. S. Porter, "Fractionation," in

Encyclopedia of Polymer Science and Technology , Vol. 7, H. F. Mark,

N. G. Gaylord, and N. M. Bikales, Eds., Interscience, NY (1967), pp. 231-260.

35
NBS-1 1 4 A 'REV. 2-80

U.s. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

81-2424

2. Performing Organ. Report NoJ 3. Publication Date

4. TITLE AND SUBTITLE

CHARACTERIZATION OF ORGANOMETALLLIC POLYMERS BY CHROMATOGRAPHIC METHODS AND NUCLEAR

MAGNETIC RESONANCE

5. AUTHOR(S)

E. J. Parks, R. B. Johannesen, and F. E. Brinckman

6. PERFORMING ORGANIZATION (If joint or other than NBS, see in struction s) 7. Contract/Grant No. NATIONAL bureau of standards

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

Naval Ship R & D Center

Annapolis Laboratory

Annapolis, MD 21402

10.

SUPPLEMENTARY NOTES

”1 Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a si gnifi cant

bibliography or literature survey, mention it here)

Organometal 1 ic polymers (OMP) are an increasingly important class of marine

surface antifouling agent undergoing intensive development by the U.S. Navy.

Candidate OMP's have been characterized at NBS by size exclusion chromatography

(SEC) coupled with tin-specific graphite furnace atomic absorption spectroscopy

(GFAA) as well as by Fourier transform nuclear magnetic resonance (FT-NMR) . The

key molecular parameters of many OMP's, the kinetics of formation of a typical

copolymer, and the effects of different concentrations of free radical initiators

on the formation of a copolymer in a well-stirred reaction system hav^-j|ll been

characterized by means of SEC-GFAA chromatograms . FT-NMR spectra of Sn have

given kinetic information in good agreement with that obtained by SEC-GFAA.' Both

chemical shift and linewidth of the tin NMR signal have been shown to have an unusually large solvent and temperature dependence. Directions for future ' research on OMP's are discussed. •

12.

KEY WORDS (Six to twelve entries ; alphabetical order; capitalize only proper names; and separate key words by semicolon s) atomic absorption spectroscopy; biocide; chromatography; copolymers; kinetics;

NMR; organometal 1 ic polymers; polymers; size exclusion chromatography; slow-release

anti foul ant.; tin.

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