Characterization of ionomer solutions. 1. Phase behavior and gelation of sulfonated polystyrene ionomers in decalin

The phase behavior of solutions of the acid form of lightly sulfonated polystyrene in Decalin was affected by the total acid group concentration and by the number of acid groups per molecule. The upper critical solution temperatures (UCST) increased with total acid group content as a consequence of poorer solvent quality. The UCST also increased with increasing number of acid groups per molecule, which was attributed to a loss of configurational entropy due to the aggregation of the acid groups by hydrogen bonding.