Thermogravimetric and Spectroscopic Characterization of Sulfonated Poly(styrene-isobutylene-styrene) Block Copolymers: Effects of Processing Conditions

Report No. ARL-TR-3803
Authors: James M. Sloan, David Suleiman, Yossef A. Elabd, Eugene Napadensky, Dawn M. Crawford
Date/Pages: May 2006; 20 pages
Abstract: In this study, sulfonated poly(styrene-isobutylene-styrene) (S-SIBS) block copolymers were characterized by thermogravimetry as a function of four different processing conditions: sulfonation level, annealing temperature, film formation, and casting solvent. Sulfonated samples showed an increase in degradation temperature from 432 to 450 ?C compared to the unsulfonated polymer, regardless of sulfonation level or other processing condition. Sulfonated samples also showed an additional minor loss of mass at ~290 ?C, which was not observed in the unsulfonated polymer. At this temperature, desulfonation or a cleavage reaction of the aromatic carbon-sulfur bond occurs. In addition, annealing the sulfonated block copolymer at a higher temperature (180 ?C) for an extended period of time also results in desulfonation. These results were confirmed by a reduction in water sorption and intensity of the infrared bands associated with sulfonic acid. There was no change in thermal stability in S-SIBS block copolymers as a function of film formation (solvent cast vs. heat pressed) and casting solvent (six different solvents).
Distribution: Approved for public release
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Last Update / Reviewed: May 1, 2006