Electrochemical and structural characterization of sulfonated polysulfone

We describe the synthesis, as well as the electrochemical and structural characterization, of sulfonated polysulfone intended for use in PEM fuel cells. Starting from a commercial polysulfone, we assessed the performance of these prepared ionomers using synthesis protocols compatible with industrial production. The efficiency of the trimethylsilyl chlorosulfonate and chlorosulfonic acid reagents in the sulfonation process was confirmed by ¹H NMR, FTIR, elemental analysis, chemical titration and thermal analysis (DSC and TGA). Chlorosulfonic acid was the most effective sulfonation reagent. However, based on SEC-MALLS, this reagent induced degradation of the backbone that is detrimental to the thermomechanical stability and lifespan of the membranes. The electrical characterization of the membranes was undertaken using impedance spectroscopy in contact with different HCl aqueous solutions at various temperatures. The activation energies, which ranged from 8.2 to 11 kJ/mol, were in agreement with the prevailing proton vehicular mechanism.