Sulfonated polyimides and their polysilsesquioxane hybrid membranes for fuel cells

Three sulfonated polyimides, including a couple of isomeric polymers, were synthesized through a typical "one pot" polymerization reaction. Hybrid membranes were constructed by incorporating a multiple-acid functionalized polysilsesquioxane into the above polymers via a sol-gel process. The properties, including thermal stability, mechanical properties, water uptake, swelling ratio, methanol permeability and proton conductivity were evaluated. The proton conductivities of the membranes were above 0.11 S cm(-1) at 100 C. Hybrid membranes exhibited the enhanced ability of water absorption and proton conducting. The methanol permeabilities of these membranes were 3.8-6.94 x 10(-7) cm(2) s(-1), which were more competitive than Nafion 117. It was found that isomeric structure could affect the properties of both the pristine and hybrid membranes. The microstructures featured with phase-separation morphology could be observed in the hybrid membranes. (c) 2014 Elsevier B.V. All rights reserved.