Thermo Stability of Highly Sulfonated Poly(styreneisobutylene-styrene) Block Copolymers: Effects 

of Sulfonation and Counter-Ion Substitution 

by James M. Sloan, David Suleiman, Eugene Napadensky, and 

Dawn M. Crawford 

ARL-TR-4357 January 2008 

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ARL-TR-4357 January 2008 

Thermo Stability of Highly Sulfonated Poly(styreneisobutylene-styrene) Block Copolymers: Effects 

of Sulfonation and Counter-Ion Substitution 

James M. Sloan, David Suleiman, Eugene Napadensky, and 

Dawn M. Crawford 

Weapons and Materials Research Directorate, ARL 

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Thermo Stability of Highly Sulfonated Poly(styrene-isobutylene-styrene) Block 

Copolymers: Effects of Sulfonation and Counter-Ion Substitution 

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James M. Sloan, David Suleiman, Eugene Napadensky, and Dawn M. Crawford 

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14. ABSTRACT 

In this study, poly(styrene-isobutylene-styrene) (SIBS) block copolymers were characterized by thermogravimetry as a function 

of sulfonation level (53% to 97%) and counter-ion substitution (Mg+2, Ca+2, Ba+2). Sulfonated samples showed an additional 

minor loss of mass at ~290 ± 2oC, which was not observed in the unsulfonated polymer. At this temperature, desulfonation or a 

cleavage reaction of the aromatic carbon-sulfur bond occurs. The counter-ion substituted membranes did not show the 

degradation temperature at 290 °C, but additional unique degradation temperatures above 500 °C, which suggests improved 

thermal stability for the ionically cross-linked polymer with cations. Some cations (Mg+2, Ca+2, Ba+2) showed multiple high 

temperature degradations, which suggest that different cross-linked structures occur throughout the phase-segregated 

morphology. 

15. SUBJECT TERMS

poly(styrene-isobutylene-styrene) block copolymers, ion-exchange membranes, cross-linked nembranes, thermogravimetric 

properties 

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19a. NAME OF RESPONSIBLE PERSON

James M. Sloan 

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ii
Contents 

List of Figures iv

List of Tables iv

1. Introduction 1

2. Experimental 2

2.1 Materials..........................................................................................................................2 

2.2 Processing Conditions.....................................................................................................2 

2.3 TGA.................................................................................................................................3 

2.4 Fourier Transform Infrared Spectroscopy (FTIR)...........................................................4 

3. Results and Discussion 4

3.1 Degradation Temperatures..............................................................................................4 

3.2 Fourier Transform Infrared Spectroscopy (FTIR)...........................................................9 

4. Conclusions 10

5. References 12

Distribution List 13 

iii
List of Figures 

Figure 1. Chemical structure of SIBS tri-block co-polymer...........................................................3 

Figure 2. TGA data for three sulfonated SIBS block co-polymers: a – 54%, b – 64%, and 

c – 97%. .....................................................................................................................................5 

Figure 3. DTGA spectra for acid forms (53%, 64%, and 97%) of SIBS........................................5 

Figure 4. Structure of SIBS-metal ion complex..............................................................................7 

Figure 5. DTGA of acid form and cation exchanged S-SIBS-53. ..................................................7 

Figure 6. DTGA data for S-SIBS-53, S-SIBS-64, and S-SIBS-97. (Curves designated with a 

are in acid form, b is neutralized with Mg+2, c is neutralized with Ca+2, and d represents 

neutralization with Ba+2.)...........................................................................................................8 

Figure 7. FTIR spectra for S-SIBS-53 membrane. (The top spectrum (a) is for S-SIBS-53-in 

acid form. The bottom spectrum (b) is for S-SIBS-53 annealed at 350 °C for 15 min. 

The IR peaks marked with asterisks are attributable to the SO3 stretching.)...........................10 

Figure 8. FTIR spectra for S-SIBS-53-Ca. (The bottom spectrum (b) is for S-SIBS-53-Ca 

before annealing at 350 °C for 15 min. The top spectrum (a) is for S-SIBS-53-Ca after 

annealing at 350 °C for 15 min. The IR peaks marked with asterisks are attributable to 

the SO3 stretching.)..................................................................................................................11 

List of Tables 

Table 1. Relationship between sulfonation level and ion-exchange capacity. ...............................3 

Table 2. Comparision of sulfonation levels for S-SIBS polymers from TGA and elemental 

analysis.......................................................................................................................................6 

Table 3. TGA degradation temperatures for cation-exchanged SIBS of different sulfonation 

levels. .........................................................................................................................................9 

iv
1. Introduction 

Phase-segregated polymers exhibit unique chemical and physical properties that can be useful in 

numerous diverse applications. This is attributable, in part, to the distinct phases that can be 

optimized to meet desired properties such as mechanical strength and permeation behavior 

resulting in a superior multifunction material (1). In addition, these materials can be chemically 

modified to engineer the material to the desired properties. 

Sulfonated block co-polymers are an example of phase-segregated polymers that are particularly 

attractive because of their potential as proton exchange membranes (PEMs) for hydrogen and 

methanol fuel cells. This application calls for the membrane to conduct protons across the ionrich domains of the polymer, while blocking the hydrogen and methanol fuel sources. For these 

membranes to be considered as PEMs, they must meet three requirements: (1) have high water 

transport properties, (2) possess low methanol permeation, and (3) exhibit excellent thermal 

stability at elevated temperatures. In this report, we address the thermal stability concern since it 

is not unusual for fuel cells to operate at 120 °C or higher. Thermogravimetric analysis (TGA) 

offers a simple and effective method for characterizing the degradation properties of these 

polymer membranes. 

One promising class of such polymers is block co-polymers, such as poly(styrene-isobutylenestyrene) (SIBS) tri-block co-polymer (2, 3). The major component of the tri-block co-polymer is 

polyisobutylene (PIB), which comprises 70% by weight of the base polymer. The PIB gives the 

material low temperature flexibility as well as excellent barrier properties. The polystyrene (PS) 

comprises 30% by weight of the material and forms a glassy region that imparts mechanical 

strength to the polymer film. In the solid state, the thermodynamic immiscibility of the two 

components results in a micro-phase separation where domains of PS are formed in the rubbery 

PIB matrix (4). The fraction of PS controls the resultant morphology, which can be for example 

cylinders, lamellae, spheres, or a complex mixture. 

Sulfonated di-block (AB) and tri-block (ABA) co-polymers have been widely researched in 

recent years. These include sulfonated polyether ether ketone (5, 6), sulfonated poly (phenylene 

oxide) (7), sulfonated polyphosphazene (8), sulfonated polybenzomidazole (9), and a variety of 

styrene-based block co-polymers (10–13). 

In addition to their use as fuel cell membranes, we are also interested in designing materials that 

can be useful as a breathable chemical protective barrier. To accomplish this, we chemically 

modify the PS units with sulfonic acid groups to form ionic domains creating ion-containing 

polymers, also called ionomers. These ionic phases are interconnected and allow for high water 

transport (14, 15), while acting as a chemical barrier to organic toxins.

1
In previous work, we have used multi-scale modeling to examine the effect of the molecular 

structure of these tri-block co-polymers on the transport properties and have found that all the 

water transport is localized in the ionic regions (16). Simulations clearly identify a phase 

separation occurring between the ionic phase (SO3

-

, H3O+, H2O) and the non-ionic region 

consisting of polyisobutylene and unsulfonated polystyrene groups resulting in a lamellar type 

structure of water molecules linked to the sulfonate groups (17). 

In this work, we evaluate the effect of using inorganic counter ions to neutralize the sulfonic acid 

groups. Our reasoning for this was to minimize the amount of swelling that the acid polymers 

exhibit. We have selected to study +2 cation-exchanged S-SIBS (Mg+2, Ca+2, Ba+2) to create 

highly cross-linked membranes. In this report, we examine the thermal stability of these 

ionomeric polymers before and after neutralization with +2 cations. 

2. Experimental 

2.1 Materials 

The poly(styrene-isobutylene-styrene) tri-block co-polymer was provided by Kuraray Co., Ltd., 

Tsukuba Research Laboratories with the reported properties: 30.84 weight-percent styrene, 

0.95 specific gravity, Mw = 71,920 g/mole, Mn = 48,850 g/mole, and poly dispersity index 

= 1.47. Other chemicals used were as follow: tetrahydrofuran (THF) (Burdick & Jackson, high 

pressure liquid chromatography (HPLC) grade, Assay 99.9%), hexanol (J.T. Baker, Assay 99%), 

toluene (VWR,* HPLC grade), and methylene chloride (Electromagnetic Science, HPLC grade). 

2.2 Processing Conditions 

The sulfonation of poly(styrene-isobutylene-styrene) was performed previously with acetyl 

sulfate as the sulfonating agent and is described in more detail elsewhere (14). Figure 1 shows 

the chemical structure for membranes prepared for this study. The mole percent of styrene 

sulfonated in each polymer was controlled by the amount of acetyl sulfate used in each reaction, 

and its exact amount was determined by elemental analysis (EA). EA was conducted by Atlantic 

Microlab, Inc., in Norcross, GA, and the results are listed in table 1. Hereafter, the sulfonated 

block co-polymers are referred to as S-SIBS-#, where S-SIBS represents sulfonated 

poly(styrene-isobutylene-styrene) and the succeeding number, #, refers to the mole percent of 

styrene sulfonated. 

 *

VWR is not an acronym. 

2
CH2 C

CH

CH

CH C

SO3H

CH2 C

x y z

Figure 1. Chemical structure of SIBS tri-block co-polymer. 

Table 1. Relationship between sulfonation level and ion-exchange capacity. 

Sample Namea Sulfonation Level 

(mol%) 

IECb

(meq/g) 

S-SIBS-0 NA NA 

S-SIBS-53 53.1 1.28 

S-SIBS-64 63.8 1.62 

S-SIBS-97 97.3 2.28 a

S-SIBS = sulfonated poly(styrene-isobutylene-styrene). b

IEC = ion exchange capacity. 

Note: NA = not applicable. 

After sulfonation, the S-SIBS samples were solvent casted in a toluene/hexanol (85/15 weightpercent) solution in an open Teflon* Petri dish for several days at ambient conditions. For 

S-SIBS-0, pure toluene was used to cast the membranes. The films were then annealed under 

vacuum at 50 °C for an additional 2 weeks to remove any residual solvent. 

The cations selected for cross-linking the membranes were Mg+2, Ca+2, and Ba+2. They were 

selected to allow ionic interactions to occur between two individual sulfonic acid groups. The 

sulfonated polymers were irreversibly cross-linked by immersion for several hours in a 1.0-M 

solution of magnesium perchlorate Mg(ClO4)2, calcium chloride CaCl2, or barium chloride 

BaCl2, depending on the desired cation. The cross-linked solutions were washed with de-ionized 

water and left to dry for at least 24 hr in a vacuum oven at 50 °C. 

2.3 TGA 

The thermal history and water loss (sorption) of the S-SIBS block co-polymers were determined 

with a high resolution TGA 2950 thermogravimetric analyzer (TA Instruments). In each 

experiment, a polymer sample weighing ~5–10 mg was used. We determined degradation 

temperatures by heating the polymer samples in a nitrogen environment to 650 °Cat 10 °C/min 

and observing regions of significant weight loss. We determined the degradation temperatures 

measured in this study by measuring each sample at least twice; the values reported correspond 

to the averages and standard deviations of those measurements. 

 *

Teflon is a registered trademark of E.I. DuPont de Nemours & Co. 

3
2.4 Fourier Transform Infrared Spectroscopy (FTIR) 

Infrared spectra of all polymer samples were collected with an FTIR spectrometer (Nicolet 

Magna 560 Series) equipped with a Thunderdome (Spectra-Tech) accessory with a singlereflection attenuated total reflectance crystal (ZnSe, refractive index = 2.4). This accessory 

contains a pressure mechanism for excellent sample-to-crystal contact. All infrared spectra were 

collected with 128 scans and 4 cm–1 resolution. 

3. Results and Discussion 

3.1 Degradation Temperatures 

Figure 2 shows the TGA spectra for three highly sulfonated functionalized S-SIBS membranes, 

53, 64, and 97 mole percent. Generally, all three curves appear similar in shape. Three weight 

loss stages can be clearly identified for the acid form. These occur at 50–200, 250–400, and 

390–475 °C. The weight loss in the 50–200 °C range can be confidently attributed to the release 

of atmospheric moisture that occurs as a result of the hydroscopic nature of the S-SIBS. The 

unusually high ionic charge of the sulfonic acid groups causes a strong ionic interaction to occur 

with the absorbed water molecules, resulting in the release of the water molecules over an 

extended temperature range. This effect can be more clearly seen if we use the derivative TGA 

(DTGA) curves presented in figure 3. From the TGA curve, one can obtain an estimate of the 

amount of atmospheric moisture that the acid form of the S-SIBS absorbs. S-SIBS-53 picks up 

9% by weight atmospheric moisture, while S-SIBS-64 picks up 10% and the S-SIBS-97 picks up 

15% water. This agrees with the highly hydroscopic nature of these systems. 

The weight loss occurring in the 250–400 °C range is attributable to the breakdown of the 

sulfonate group attached to the styrene rings. This assignment agrees with data published by 

Smitha et al. (18) for sulfonated polystyrene. From the TGA curves in figure 2, we can also 

estimate the amount of sulfonate groups present in the functionalized SIBS. To do this, it is first 

necessary to subtract the moisture content from the TGA spectra and then calculate for sulfonate 

groups. The general formula is SnIBmSn, where S stands for a monomer of styrene and IB is a 

monomer of isobutylene. Since the monomer weights are about 104 and 56 g/mole for styrene 

and isobutylene, respectively, one can calculate that the corresponding molecular formula should 

be approximately S73IB602S73. For the sulfonated forms, SO3H (MW = 81) is added in 

proportional amounts to determine an estimate of weights. Table 2 shows a comparison of 

calculated and experimentally determined sulfonate levels. Generally, good agreement is 

observed between the calculated and experimentally determined sulfonation levels; however, a 

slight deviation is seen at the higher sulfonate levels.

4
0

10

20

30

40

50

60

70

80

90

100

50 100 150 200 250 300 350 400 450 500 550 600 650 700

a

c

b

Figure 2. TGA data for three sulfonated SIBS block co-polymers: a – 54%, b – 64%, and 

c – 97%. 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

100 200 300 400 500 600

Derivative Weight

Temperature

420o C

Figure 3. DTGA spectra for acid forms (53%, 64%, and 97%) of SIBS. 

5
Table 2. Comparision of sulfonation levels for S-SIBS polymers from TGA and elemental analysis. 

Sample Name 

Sulfonation Level 

(Weight-Percent) Calculated 

Sulfonation Level 

(Weight-Percent) Experiment 

S-SIBS-0 NA NA 

S-SIBS-53 11.1 12.0 

S-SIBS-64 12.9 15.1 

S-SIBS-97 18.4 21.3 

Note: NA = not applicable. 

The last weight loss region occurring at 390–475 °C is attributable to the decomposition of the 

polystyrene and polyisobutylene segments. A close examination of figure 3 reveals that this 

broad peak centered at ~455 °C has two components, one small peak at ~420 °C and one 

centered at 455 °C. The small peak at ~420 °C is attributable to the polystyrene block 

decomposition. Other authors have reported similar maxima for sulfonated polystyrene (18). 

The weight loss at 455 °C is attributable to the polyisobutylene block decomposition. In many of 

the TGA spectra, these two bands overlap and are nearly indistinguishable from each other. 

We now turn our attention to the cation neutralized polymer membranes. The membranes were 

neutralized in an attempt to dimensionally stabilize the polymer by introducing cross-links into 

the structure to reduce the water swelling (figure 4). For example, the S-SIBS-64 membrane 

could take more than 300% by weight of water (14). In figure 5, four different films are shown: 

the acid form of S-SIBS-53 and three ionically exchanged films with Mg+2, Ca+2, and Ba+2. The 

DTGA of the cation exchanged films in figure 5 shows three weight loss stages as well. These 

occur at 50–200, 425–475, and 475–600 °C. The first two weight loss stages are identical to the 

acid form ionomer, loss of atmospheric moisture and decomposition of polyisobutylene 

backbone. The weight loss at 300 °C is noticeably absent in these curves; however, a new 

weight loss region is now observed around 475–600 °C. Other investigators (18) have postulated 

that this weight loss may be attributable to chain splitting or residual solvent. In our 

experiments, we have observed that this weight loss has been observed for all cation exchanged 

samples, while no high temperature loss has been observed in any of the acid forms. 

Additionally, the lack of sulfonate decomposition at 250–400 °C seems to suggest that this loss 

is attributable to the decomposition of the styrenic groups that are ionically associated to the 

individual cations. These clusters have the ability to thermally stabilize the entire polymer 

membrane by shifting the degradation temperature to 450 °C. 

Figure 6 presents the DTGA data comparing the three sulfonation levels and corresponding 

cation neutralized forms. The higher temperature weight loss region can be clearly seen in 

figure 6. We note that multiple peaks are evident above 500 °C for the Mg+2 and Ca+2 forms, 

which suggests that different cross-linked structures occur throughout the phase-segregated 

morphology. These structures appear to vary in thermal stability. The case of the Ba+2 neutralized 

forms is slightly different in that only one detectable peak is evident and this peak is shifted to a 

lower temperature at around 500 °C. Again, this position is driven by the strength of the 

localized environment.

6
M

S

O

O

O

S

O

O

O

Figure 4. Structure of SIBS-metal ion complex. 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

100 200 300 400 500 600 700

Derivative Weight

Temperature

S-SIBS-53

Acid

Ba

Ca

Mg

Figure 5. DTGA of acid form and cation exchanged S-SIBS-53. 

7
50 100 150 200 250 300 350 400 450 500 550 600 650

Temp (C)

Derivative Weight (%/C)

50 100 150 200 250 300 350 400 450 500 550 600 650

Temp (C)

Derivative Weight (%/C)

50 100 150 200 250 300 350 400 450 500 550 600 650

Temp (C)

Derivative Weight (%/C)

S-SIBS-53 

S-SIBS-64 

S-SIBS-97 

a 

a 

a 

b 

b 

b 

d 

c 

c 

d 

d 

c 

Figure 6. DTGA data for S-SIBS-53, S-SIBS-64, and S-SIBS-97. (Curves 

designated with a are in acid form, b is neutralized with Mg+2, c is 

neutralized with Ca+2, and d represents neutralization with Ba+2.) 

8
Figure 6 also shows an increase in the size of the weight loss in the high temperature region with 

increasing sulfonation levels, thus yielding further evidence that these weight loss maxima are 

directly related to the ionic complexes formed as a result of the cation-sulfonate group 

interactions. 

A summary of the degradation temperatures for all the membranes studied is presented in table 3, 

excluding the hydroscopic region. As in our previous communication (19), the sulfonated unneutralized samples reveal two separate degradation temperatures, one at ~290 ± 5 °C, attributable 

to sulfonic acid loss and another at ~453 ± 3 °C, attributable to polymer backbone. The location 

of the 290 and 453 °C are identical, regardless of sulfonation level. All neutralized sulfonated 

polymers show two degradation temperatures, one occurring at 453 ± 3 °C, attributable to polymer 

backbone and another in the 500–600 °C range, attributable to the counterion-sulfonic acid 

complex. The locations of the peak maxima at 453 °C and the transitions above 500 °C are 

identical, regardless of sulfonations level or counterion type. 

Table 3. TGA degradation temperatures for cation-exchanged SIBS of different sulfonation levels.

Sample Name 

First 

Degradation 

Temperature 

(°C) 

Second 

Degradation 

Temperature 

(°C) 

Third 

Degradation 

Temperature 

(°C) 

Fourth 

Degradation 

Temperature 

(°C) 

Fifth 

Degradation 

Temperature 

(°C) 

S-SIBS-53-H 290 ± 5 454 ± 2 — — — 

S-SIBS-53-Mg — 451 ± 2 507 ± 2 604 ± 2 — 

S-SIBS-53-Ca — 453 ± 1 592 ± 2 — — 

S-SIBS-53-Ba — 450 ± 1 481 ± 2 — — 

S-SIBS-64-H 290 ± 5 455 ± 2 — — — 

S-SIBS-64-Mg — 453 ± 2 521 ± 3 606 ± 3 — 

S-SIBS-64-Ca — 456 ± 2 517 ± 2 586 ± 2 — 

S-SIBS-64-Ba — 455 ± 1 502 ± 2 582 ± 3 — 

S-SIBS-97-H 290 ± 5 449 ± 2 — — — 

S-SIBS-97-Mg — 454 ± 2 536 ± 3 570 ± 4 594 ± 2 

S-SIBS-97-Ca — 454 ± 1 532 ± 2 585 ± 3 — 

S-SIBS-97-Ba — 457 ± 1 505 ± 2 — — 

3.2 Fourier Transform Infrared Spectroscopy (FTIR) 

In order to confirm the identification of the higher temperature thermal weight loss transitions, 

FTIR was used to identify the chemical structures remaining in the polymer membrane. Figure 7 

shows the S-SIBS-53 membrane before and after annealing at 350 °C for 15 min. The bands 

associated with the SO3 group (1007, 1034, and 1125 cm–1) are identified with asterisks and can 

clearly be observed decreasing when the membrane is annealed at 350 °C. 

9
Figure 7. FTIR spectra for S-SIBS-53 membrane. (The top spectrum (a) is for S-SIBS-53-in acid form. 

The bottom spectrum (b) is for S-SIBS-53 annealed at 350 °C for 15 min. The IR peaks marked 

with asterisks are attributable to the SO3 stretching.) 

In contrast to this effect, figure 8 shows the corresponding spectra for the S-SIBS-53-Ca 

membrane. In this case, the three bands associated with the SO3 group do not disappear; in fact, 

they remain unchanged. This indicates that the new ionic cross-link structures are thermally 

more stable than their acidic counterpart. 

4. Conclusions 

We have studied the degradation of highly sulfonated S-SIBS block co-polymers and three cation 

neutralized forms, Mg+2, Ca+2, and Ba+2. The acid forms show low temperature degradation 

because of the release of the sulfonate groups. This amount of the weight loss increases with 

increasing sulfonation levels, but the position remains unchanged. All counter-ion neutralized 

polymers show a shift of this degradation of almost 300 °C. This is because of a unique and 

robust complex formed between the sulfonate groups and metal cations. We have used FTIR to 

verify that the sulfonate linkages degrade at ~300 °C. However, in the counter-ion neutralized 

forms, this degradation is shifted to ~550 °C, while the polymer backbone still degrades at 450 °C.

10
-

A 

 1500 1400 1300 1200 1100 1000 900 800 700 

Cm-1 

S-SIBS-53-Ca 

a 

b 

* *

*

Figure 8. FTIR spectra for S-SIBS-53-Ca. (The bottom spectrum (b) is for S-SIBS-53-Ca before annealing 

at 350 °C for 15 min. The top spectrum (a) is for S-SIBS-53-Ca after annealing at 350 °C for 

15 min. The IR peaks marked with asterisks are attributable to the SO3 stretching.) 

11
5. References 

1. Holden, G.; Kricheldorf, H. R.; Quirk, R. P. Thermoplastic Elastomers; 3rd ed.; Hanser 

Publishers: Munich, 2004. 

2. Storey, R. F.; Chisholm, B. J.; Lee, Y. Polymer Eng. and Sci. 1997, 37, 73. 

3. Crawford, D. M.; Napadensky, E.; Tan, N. C.; Reuschle, D. A.; Mountz, D. A.; Mauritz, 

K. A.; Laverdure, K. S.; Gido, S. P.; Liu, W.; Hsiao, B. Thermochim Acta 2001, 367, 125. 

4. Lu, X.; Steckle, W. P.; Weiss, R. A. Macromolecules 1993, 26, 5876. 

5. Lakshami, V. V.; Choudhary, V.; Varma, I. K. Macromol Symp. 2004, 210, 21. 

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7. Schauer, J.; Albrecht, W.; Weigel, T. J. Appl. Poly Sci. 1999, 73, 161. 

8. Guo, Q.; Pintauro, P. N.; Tang, H.; O’Connor, S. O. J. Membrane Sci. 1999, 154, 175. 

9. Jones, D.; Roziere, J. J. Membr Sci. 2004, 185, 41. 

10. Weiss, R. A.; Sen, A.; Willis, C. L.; Pottick, L. A. Polymer 1991, 32, 1867. 

11. Weiss, R. A.; Sen, A.; Pottick, L. A.; Willis, C. L. Polymer 1991, 32, 2785. 

12. Serpico, J. M.; Ehrenberg, S. G.; Fontanella, J. J.; Jiao, X.; et al. Macromolecules 2002, 35, 

5916. 

13. Mani, S.; Weiss, R. A.; Williams, C. E.; Hahn, S. F. Macromolecules 1999, 32, 3663. 

14. Elabd, Y. A.; Napadensky, E. Polymer 2004, 45, 3037. 

15. Elabd, Y. A.; Napadensky, E.; Sloan, J. M.; Crawford, D. M.; Walker, C. W. J. of 

Membrane Sci. 2003, 217, 227. 

16. Andzelm, J.; Sloan, J. M.; Napadensky, E.; McKnight, S.; Rigby, D. Proceedings AIChE 

Annual Meeting, 2005. 

17. Andzelm, J.; Sloan, J. M.; Napadensky, E.; McKnight, S.; Rigby, D. Molecular Simulation

2006, 32, 163. 

18. Smitha, B.; Sridhar, S.; Khan, A. A. J. of Membrane Sci. 2003, 225, 63. 

19. Suleiman, D.; Elabd, Y. A.; Sloan, J. M.; Napadensky, E.; Crawford, D. M. Thermochimica 

Acta 2005, 430, 149.

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 2800 POWDER MILL RD 

 ADELPHI MD 20783-1197 

ABERDEEN PROVING GROUND

 1 DIR USARL 

 AMSRD ARL CI OK TP (BLDG 4600) 
NO. OF 

COPIES ORGANIZATION 

14

 5 US ARMY SBCCOM 

 SOLDIER SYSTEMS CTR 

 W ZUKAS 

 M SENNETT 

 Q TRUONG 

 E WILUSZ 

 J VARNUM 

 KANSAS ST 

 NATICK MA 01760-5012 

ABERDEEN PROVING GROUND

 21 DIR USARL 

 AMSRD ARL WM 

 J SMITH 

 AMSRD ARL WM M 

 S MCKNIGHT 

 AMSRD ARL WM MA 

 M VANLANDINGHAM 

 L GHIORSE 

 R JENSEN 

 D FLANAGAN 

 P TOUCHET 

 H FEUER 

 C PERGANTIS 

 J SLOAN (10 CPS) 

 E NAPADENSKY 

 D CRAWFORD