Highly fluorinated poly arylene ethers containing sulfonated naphthol pendants with improved proton conductivity as a polymer electrolyte for proton exchange membrane fuel cells

To evaluate a more straightforward procedure for the synthesis of proton exchange polymers with enhanced proton conductivities, four series of poly arylene ethers (PAEs) with different contents of disulfonated naphthol pendant groups were synthesized in a two-step nucleophilic substitution reaction. The structure of base PAEs and consequent sulfonated derivatives were characterized by 1H NMR and FT-IR spectroscopy. After the preparation of membranes from synthesized copolymers, their properties including ion exchange capacity, water uptake, swelling ratio, proton conductivity (PC), mechanical stability, thermal, and oxidative stability were evaluated. Data indicate that the molecular weight of synthesized base polymers has played a vital role in the properties of prepared membranes. It was also observed that the structure of incorporated biphenol in the synthesis of copolymers affects the properties of the resulting membranes even in similar proton conductivities. Among the four different structures of synthesized copolymers, the membranes based on bisphenol AF, which contained the highest amount of fluorine groups in the structure, showed the best properties. The sample Dec-AF-3 displayed a good fuel cell performance at 80 °C with a current density of 1130 mA/cm2 and a maximum power density of 332 mW/cm2.