Fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) for fuel cell applications

A series of fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) were synthesized via aromatic nucleophilic substitution polymerization. The sulfonation content (SC) was controlled by the feed ratios of sulfonated and nonsulfonated monomers. Flexible and strong membranes in the sulfonic acid form were obtained from cast membranes in the sodium salt forms by treatment with acid. The thermal properties, water uptake, swelling ratio, water state, oxidative stability, proton conductivity and methanol permeability were investigated. All the polymers had proton conductivities greater than 1 × 10−2 S/cm at room temperature, and the conductivity values of m-SPFEEKK-80 and p-SPFEEKK-80 were up to 1.86 × 10−1 and 1.78 × 10−1 S/cm at 100 °C. This series of polymers also possessed good dimensional stability in water and low methanol crossover.