Recent Developments in Aromatic Polymer-Based Proton Exchange Membranes

Abstract

A significant amount of research has been carried out on the preparation, fabrication of membranes, and evaluation of properties of proton exchange membranes (PEM) for fuel cell applications. This book chapter is dedicated to the recent progress of aromatic polymer-based PEMs with various molecular designs as an alternative to conventional perfluorinated polymers. Aromatic sulfonated polymers such as poly(arylene ether)s, polyamides, polytriazoles, and polybenzimidazoles have established themselves as strong contenders in the PEM portfolio for their unique sets of physical and chemical properties. The enhancements of proton conductivity under hydrated conditions and at elevated operating temperatures are essential for harnessing the efficiency of the aromatic PEM materials. The design of polymers with fluorinated and non-fluorinated bulky groups as hydrophobic segments has shown great promise in this direction. The strategies in obtaining highly interconnected ionic channels for proton conduction and retention of water through microphase separation between hydrophilic and hydrophobic domains while increasing the ion exchange capacity of PEMs are discussed. The significant efforts of our group's research to develop fluorinated, non-fluorinated, phosphorous-containing sulfonated polymer membranes for PEM applications are also discussed in this book chapter.