Enhanced proton conductivity of poly(ether sulfone) multi-block copolymers grafted with densely pendant sulfoalkoxyl side chains for proton exchange membranes

Abstract

A series of proton exchange membranes were prepared from poly(ether sulfone) multi-block copolymers grafted with densely pendent sulfoalkoxyl side chains for fuel cell applications. Each polymers contains four pendent sulfonic acids per unit. The chemical structures were confirmed by 1H NMR and FTIR spectroscopy, providing evidence of complete methoxy conversion and sulfobutylation. The introduction of densely grafted flexible pendent side chains to the block structure was effective to enhance phase separation and thus form broader hydrophilic channels. These membranes displayed considerably improved proton conductivities especially at low RH conditions. Furthermore, these membranes also showed promising fuel cell performance both at 20% and 80% RH conditions. In comparison to Nafion 212 membranes, the present membranes displayed enhanced swelling behavior, mechanical strength, proton conductivity, and fuel cell performance, demonstrating that they can be an alternative PEM to perfluorosulfonic acid polymers.