Self-assembled sulfonated block copolymer semipermeable membrane and uses therefor

Abstract

A semipermeable membrane that is capable of remaining flexible at a temperature of at least −60° C. is selective to liquid penetrants depending on the size and polarity of the penetrants, and more specifically, the membrane has sufficient selectivity so as to be capable of allowing water to diffuse therethrough at a higher rate than virtually all organic liquids having a molecular weight higher than that of methanol. The semipermeable membrane, which is produced from an unsulfonated block copolymer having polystyrene and polyisobutylene segments, includes a sulfonated block copolymer including poly (styrene-co-styrene sulfonic acid) segments and polyisobutylene segments. Prior to modification by sulfonation, the unsulfonated polystyrene and polyisobutylene block copolymer includes polystyrene monomer in an amount of from 5% to 90% by weight of the total unsulfonated block copolymer. After modification, from 1 to 70 mole % of the polystyrene monomer in the unsulfonated polystyrene and polyisobutylene block copolymer is converted to styrene sulfonic acid in the sulfonated block copolymer. By virtue of the semipermeable membrane's excellent transport and mechanical properties, and ease of processing, the various embodiments of the membrane advantageously find numerous uses, including in chemical and/or biological protective apparel, as an ion-conducting membrane for use in a fuel cell, and in medical equipment and apparel.