Solution processable octa(aminophenyl)silsesquioxane covalently cross-linked sulfonated polyimides for proton exchange membranes

In this work, a series of octa(aminophenyl)silsesquioxane(OAPS) covalently cross-linked sulfonated polyimides (SPIs) were fabricated for improving their mechanical and chemical stability, reducing fuel crossover and improving proton conductivity as proton exchange membranes. The content of OAPS cross-linkers was modified from 0.2 to 1.6 mol% to control the degree of cross-linking. The resulting OAPS cross linked membranes were solution processable and exhibited higher strength, superior thermal and chemical stabilities, and lower methanol permeability compared with the linear SPI membrane. Compared with Nafion 117, all of the cross linked membranes exhibited comparable proton conductivity from 20 to 80 degrees C and at 100% relative humidity. Moreover, when the content of OAPS was 0.4 mol%, the cross linked SPI exhibited the highest proton conductivity (0.111 S/cm). (C) 2014 Elsevier B.V. All rights reserved.