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

摘要

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 degrees 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 degrees 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 degrees 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).