Thermo Stability of Highly Sulfonated Poly(styrene-isobutylene-styrene) Block Copolymers: Effects of Sulfonation and Counter-Ion Substitution

Report No. ARL-TR-4357
Authors: James M. Sloan; David Suleiman; Eugene Napadensky; Dawn M. Crawford
Date/Pages: January 2008; 20 pages
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 ¿ 2¿C, 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.
Distribution: Approved for public release
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Last Update / Reviewed: January 1, 2008