Fluorinated poly(ether sulfone) ionomers with disulfonated naphthyl pendants for proton exchange membrane applications

Abstract

Proton exchange membranes based on fluorinated poly(ether sulfone)s with disulfonated naphthyl pendants (sSPFES) have been successfully prepared by post functionalization through polymeric S_NAr reaction. Copolymer structure was confirmed by H-nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy, the physico-chemical properties of the sSPFES membranes were evaluated by thermogravimetric analysis, gel permeation chromatography, electro-chemical impedance spectroscopy, atomic force microscopy, Fenton, water-swelling and fuel cell test. The pendant grafting degree was controlled by varying the feeding amount of the disulfonaphthols, resulting in the ion exchange capacity about 1.28-1.73 mmol/g. The obtained sSPFES membranes were thermal stable, mechanical ductile, and exhibited dimensional change less than 17%, water uptake below 70%, and proton conductivity as high as 0.17-0.28 S/cm at 90°C in water. In a single H₂/O₂ fuel cell test at 80°C, the sSPFES-B-3.2 membrane (1.61 mmol/g) showed the maximum power output of 593–658 mW/cm² at 60%-80% relative humidity, indicating their rather promising potential for fuel cell applications.