Polymer electrolyte membranes based on poly(arylene ether)s with penta-sulfonated pendent groups

Abstract

The preparation and characterization of new polymeric ionomers based on a fully aromatic poly(arylene ether) backbone with locally pentasulfonated pendent groups for applications as proton exchange membranes is reported. The high molecular weight sulfonated polymers were obtained by the polycondensation of new (2,6-difluorophenyl) (4-(1,2,3,4,5-pentaphenylbenzene)phenyl)methanone, 4,4′-difluorodiphenyl methanone, and 4,4′-dihydroxydiphenylsulfone, followed by sulfonation using sulfuric acid in high yields. The polymers produced tough, flexible, and transparent membranes by solvent casting. Membranes with ion exchange capacities between 0.8 and 1.7 mEq g^-1 showed high proton conductivities and low methanol permeabilities. Compared to Nafion 117, these sulfonated membranes exhibited better microphase separation morphologies. The fully humidified membranes also exhibited considerably good mechanical properties, with tensile strengths from 35 to 45 MPa and elongations at break from 23 to 49%. This investigation demonstrates a controllable high density sulfonated side group of a poly(arylene ether sulfone) membrane with tunable and balanced properties, which is promising for proton exchange membrane fuel cell technology.