Cross-Linked Sulfonated Poly(arylene ether sulfone) Membranes Formed by <i>in Situ</i> Casting and Click Reaction for Applications in Fuel Cells

Abstract

Sulfonated poly­(arylene ether sulfone) membranes with cross-linked structures (C-SPAES) were simply prepared by simultaneously casting and heating the polymer solutions composed of sulfonated poly­(arylene ether sulfone) with azidomethyl side groups (SPAES-N₃), cross-linkers such as 1,4-diethynylbenzene and 4,4′-diazido-2,2′-stilbenedisulfonic acid disodium salt tetrahydrate, and a click reaction catalyst such as CuBr and <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>″,<i>N</i>″-pentamethyldiethylenetriamine in <i>N</i>,<i>N</i>-dimethylacetamide, where SPAES-N₃ were prepared by the substitution of sulfonated PAES (SPAES) through chloromethylation followed by azidation reaction. C-SPAES membranes obtained using the optimum amount of the cross-linkers showed much improved chemical and physical stabilities and mechanical strength compared with linear SPAES membrane. Since the cross-linked structures were formed by the cross-linker having sulfonic acid groups, C-SPAES membranes showed higher ion exchange capacity and proton conductivity than the linear SPAES membrane. Although the C-SPAES membrane can absorb more water than the linear SPAES membrane, less volume expansion was observed due to their physically stable cross-linked structures