Abstract
Rigid-rod poly(p-phenylene sulfonic acids) were shown to have "frozen-in" free volume that enabled them to retain water at low relative humidity, generating very high conductivity; the best was 0.1 S/cm at 15% RH and 75C. Efforts to generate dimensional stability by grafting alkyl benzenes on the polymers worked well for poly(biphenylene disulfonic acid). Poly(phenylene disulfonic acid) grafting has not yet produced water stable PEMs.