Ionomers for proton exchange membrane fuel cells with sulfonic acid groups on the end-groups:: Novel branched poly(ether-ketone)s with 3,6-ditrityl-9H-carbazole end-groups

A study was conducted, to demonstrate the effect of branched polyether ketones with 3,6-Ditrityl-9H-Carbazole end-groups on ionomers for proton exchange membrane fuel cells. The end-groups were synthesized with an aromatic electrophilic substitution reaction of 9H-carbazole, with trityl chloride, by heating at 220-230 °C for 0.7 hours. The study also employed 1,3,5-Tris(4-(4-fluorophenylsulfonyl)benzene, as the trifunctional branching agent, diphenol, and aromatic difluorides as monomers for the synthesis of wholly aromatic, chemically stable, and soluble blocks. It was found that these blocks were stable under the sulfonation conditions, due to the introduction of strong electron-withdrawing group, such as a ketone group, or sulfonyl group on each phenylene ring. A model reaction was also conducted, to compare the reactivity of carbazole and the phenol.