Synthesis and characterization of sulfonated poly(arylene thioether)s and their blends with polybenzimidazole for proton exchange membranes

A series of sulfonated poly(arylene thioether)s were successfully prepared via nucleophilic displacement of aromatic dihalides with thiomonomers (4,4′-thiodiphenol or 4,4′-thiobisbenzenethiol) in the presence of excess of potassium carbonate. The synthesized polymers were characterized by NMR spectroscopy, gel permeation chromatography (GPC) and thermogravimetric analysis. Proton exchange membranes were prepared from blends of the sulfonated poly(arylene thioether)s and polybenzimidazole (PBI) and investigated in terms of water uptake and swelling, proton conductivity and oxidative chemical stability. PBI-sulfonated polymer blend membranes had a room temperature proton conductivity in the range 0.12–0.22 S/cm and exhibited lower water uptakes and better chemical stability against hydrogen peroxide treatment as compared to that of pure sulfonated polymer membranes. The membrane prepared from the blend of sulfonated poly(arylene thiosulfone)s and PBI showed excellent oxidative stability, displaying no weight loss for 45 h in 5 wt% hydrogen peroxide solution at 60 °C.