Macromolecules, 2019, vol 52, 6, pp. 2548-2559
We systematically investigated the effect of incorporating a sterically hindered pyridyl group into a sulfo-phenylated polyphenylene to control the polymers physicochemical properties through acidbase interactions. Homopolymers with similar molecular weights and comparable structures that vary by only one atom (N vs C?) per repeat unit along the polymer chain were prepared. Compared to a non-pyridyl reference membrane, incorporation of a pyridyl group improves the oxidative stability against free radicals, increases the elongation at break to 55% (from 37%), and enhances the thermal stability to 326 °C (from 246 °C). In an accelerated fuel cell degradation test, polymeric membranes containing the sterically encumbered pyridyl unit exhibited exceptional stability (0.16 mV h1 degradation rate over 1000 h) and retained ?80% of their peak power density over this time.