Polymer electrolyte characteristics of Sulfonated block-graft polyimide membranes: Influence of block ratio

Abstract

A series of sulfonated polyimides (SPIs) composed of block- or random-graft structures with different block ratios were synthesized for the application to polymer electrolyte membrane fuel cells. Four types of SPIs were successfully obtained with similar ion exchange capacity (IEC) values to discuss the influence of block-graft structures and block ratios on polymer electrolyte characteristics including proton conductivity, water uptake, and gas barrier property. Among the four SPI membranes, the SPI bearing high hydrophilic block ratio and low grafting hydrophilic side-chain ratio showed highest proton conductivity and best gas barrier property. This study revealed that the block ratio of main-chain has a significant role on the characteristics of the SPI membranes. These novel SPI membranes, which showed better proton/oxygen selectivity than a conventional Nafion membrane, have potential applications for future fuel cells.