Sulfonated poly(arylene thioether phosphine oxide)/sulfonated benzimidazole blends for proton exchange membranes

Sulfonated poly(arylene thioether phosphine oxide)s (sPATPO) with high ion exchange capacity generally shows excessive swelling, hampering their application as proton exchange membranes. To reduce their swelling, they were blended with sulfonated benzimidazoles (sPBIs) because they could form strong intermolecular interactions with sPBIs. Such sulfonated benzimidazoles should exhibit excellent solubility so as to prevent the formation of precipitate during the blend process. In order to achieve sPBI with high solubility, high content hexafluoroisopropylidene moieties were incorporated into the polymer backbone by polycondensation. The sPATPO/sPBI blend membranes present high thermal stability. More importantly, they show low swelling while maintaining high proton conductivity. At the same time, their oxidative stability is remarkably increased and their mechanical properties are also improved. As a result, these blend membranes indicate excellent comprehensive properties.

Research highlights
► sPATPO/sPBI blend membranes were prepared and evaluated as PEMs for the first time.
► The strong interactions between sPATPO and sPBI greatly reduce the swelling of the blends.
► sPATPO/sPBI blend membranes exhibit excellent overall properties.