Alternative polymer systems for proton exchange membranes (PEMs)

This review covers the materials requirements for advanced alternative proton exchange membranes for fuel cells, assesses recent progress in this area, and provides directions for the development of next-generation materials. Focus is on the synthesis of polymeric materials that have attached ion conducting groups. First, state-of-the-art Nafion and its commercially available perfluorosulfonic acid relatives are discussed. Second, the large body of recent literature centered on polymeric materials based on step or condensation polymers and various strategies for incorporating ionic groups into these materials are evaluated. Finally, the synthetic aspects of ion conducting polymers and the polymer chemical structure considerations for producing useful PEMs are presented.