Poly(ether ether ketone) grafted with sulfoalkylamine as proton exchange membrane

A series of side-chain-type sulfonated poly(arylene ether ketone)s with high ion exchange capacity (IEC) values were prepared by polycondensation reaction of 4,4′-difluorobenzophenone with 2,2′-bis(3-amino-4-hydroxyphenyl) and bisphenol A, followed by post-grafting reaction using 1,4-butanesultone. For these obtained membranes, sulfoalkylamine functionalized poly(ether ether ketone) (SAm-PEEK)-0.8 with the highest IEC of 3.42 mequiv. g−1 displayed the highest proton conductivity of 0.11 S cm−1 at 25°C and 0.167 S cm−1 at 60°C, respectively. The morphology of these membranes was investigated by transmission electron microscope analysis. The result showed that these membranes exhibited well-connected hydrophilic channels due to their high IEC values and densely populated flexible acid side chains. Owing to their low methanol permeability and high selectivity, SAm-PEEK-x membranes are promising candidates for direct methanol fuel cell applications.