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Abstract Summary: A series of branched and cross‐linked poly(arylene ether sulfone) ionomers containing sulfofluorenyl groups, 2b–e were synthesized in order to investigate the effect of these chemical modifications on the properties. Ionomers 2b–e gave a flexible, ductile, and transparent membrane by casting from DMAc solution. The branching and cross‐linking were effective to improve the dimensional stability under wet conditions without losing their high thermal, oxidative, and hydrolytic stability. The cross‐linked ionomer 2e (IEC = 2.63 meq · g −1 ) membrane showed high proton conductivity of 0.2 S · cm −1 at 87% RH and 0.02 S · cm −1 at 57% RH. The branched ionomer 2b membrane was durable in proton conductivity for almost 2 months without any chemical degradation. Chemical structure of branched and cross‐linked poly(arylene ether sulfone) ionomers. magnified image Chemical structure of branched and cross‐linked poly(arylene ether sulfone) ionomers.
Chikashige et al. (Mon,) studied this question.