Preparation and properties of novel sulfonated poly(arylene ether ketone) random copolymers for polymer electrolyte membrane fuel cells

Two series of novel poly(arylene ether ketone)s were prepared using direct copolymerization of 3,3′-disulfonated-4,4′-difluorobenzophenone (SDFB) as synthesized sulfonated dihalide and difluorobenzophenone (DFB) as nonsulfonated dihalide monomer with 4,4′-(1,4-phenylene diisopropylidene) bisphenol (BP) or 4,4′-(1,3-phenylene diisopropylidene) bisphenol (BM). Copolymers were synthesized by polycondensation in different degrees of sulfonation (25–45%). 1H NMR and FT-IR spectroscopy, dynamic mechanical thermal analysis, thermogravimetric analysis, and tensile test were used for characterization of prepared membranes. Inherent viscosity of synthesized copolymers was between 1.08 and 2.63 dL/g. Copolymers showed acceptable properties as proton exchange membrane for fuel cells. Ion exchange capacity of membranes was between 0.76 and 1.46 meq/g. Membranes showed proton conductivities increased by increasing in degree of sulfonation and reached to 0.08 S/cm. Prepared membranes were thermally stable up to 260 °C and water uptake of these samples were in the range of 11–27 wt%.