Sulfonated block polyimide copolymers as a proton-conductive membrane

The synthesis of a series of block sulfonate polyimide (SPI) ionomers to control hydrophilic and hydrophobic phase separation for the improvement of the proton conductivity at low humidity conditions, is presented. The new block SPI-B ionomer membranes showed chemical stability comparable to that of SPI-R equivalent. The block/block copolymer SPI-B150/150 membrane, containing long block segments in both the hydrophilic and the hydrophobic components, showed the highest proton conductivity. STEM observations confirmed widespread and well-connected hydrophilic domains, which proves the high proton-transporting properties of the SPI-B150/150.