Polymer electrolyte membranes based on poly(arylene ether)s with flexible disulfophenyl pendant

•Poly(arylene ether)s containing flexible disulfonic acid pendant was synthesized.•The I-50 exhibited comparable conductivity to Nafion 117 and lower swelling ratio.•Disulfonic acid side chain I-x was better than SP-90 with similar IEC value.

New difluoride monomer containing a biphenyl pendant group is designed and synthesized for preparing side chain style polyelectrolyte. As a result, a novel poly(arylene ether)s containing flexible disulfonic acid pendant are obtained by a two-step synthetic procedure. First, poly(arylene ether)s with electron-rich side groups as polymer precursor (P-x) are prepared from designed difluoride monomer, 4,4′-difluorobenzophenone (DFDPK), and 4,4′-(hexafluoroisopropylidene)diphenol (6FBPA) by nucleophilic polycondensation. Then objective sulfonated polymers (I-x) are obtained from P-x and chlorosulfonic acid by sulfonation reaction. Tough, flexible, and transparent membranes having high mechanical strength are obtained by solution casting of I-x polymer. The membrane I-x exhibits high proton conductivity and good dimensional stability, which attributes their special side chain style structure. For example, I-50 membrane (IEC = 1.32 meq. g−1) shows low swelling of 8.1% and comparable conductivity with Nafion 117 at 80 °C. Suitable morphology is observed in I-x membranes by SAXS test, which may explain that I-x possess perfect overall properties.