Polyimide-based Electrolyte Modified with Siloxane Segments for Proton Transportation

摘要

Various sulfonated aromatic polymers, such as poly(aryl ether sulfone)s~( 3-6) poly(ether ketone),~(7,8) polyimide (PI),~(9-18) polybenzimidazole (PBI) ~(19-23) etc. have been proposed as alternative membrane materials. However, most of such sulfonated aromatic polymers and acid-doped polymers have lower proton conductivity as compared to that of Nafion although few of them exhibit enhanced mechanical properties or lower methanol permeability. The proton conductivity of polymer membranes depends on the chemical structure of the polymer, ion exchange capacity (IEC), water uptake and hydrated morphology. The study of phase separation in polymer electrolyte membranes has emphasized the significance of formation of ionic channels to improve the proton conductivity. Nafion is made with a polytetrafluoroethylene backbone and perfluorinated vinyl ether pendant side chains terminated by a sulfonate ionic group.24