Wholly aromatic five- and six-membered ring polyimides containing pendant sulfonic acid functional groups

Abstract

A series of high molecular weight five- and six-membered ring polyimides containing controlled degree of pendant sulfonic acid groups were synthesized from 4,4′-diamino-biphenyl-2,2′-disulfonic acid (DBS) sulfonated monomer. Solution cast films of the sulfonated polyimide membranes gave tough-ductile membranes and demonstrated moderate to high water absorption. Solution cast sulfonated polyimide membranes were aged in an oven at increasing temperatures for 30 min and then titrated with TMAH. All the aged films were completely dissolved in DMAc up to 240°C and gave similar IEC values.