Effect of Fluorene Groups on the Properties of Multiblock Poly(arylene ether sulfone)s-Based Anion-Exchange Membranes

摘要

Two kinds of novel multiblock poly(arylene ether sulfone)s were synthesized via block copolycondensation of telechelic oligomers as a starting material for the preparation of anion-exchange membranes (AEMs). The as-synthesized copolymers have extremely similar main chains. The difference is that the benzylmethyl groups for one are located on the fluorene—sulfone segments and they are located on the isopropylidene—sulfone segments for the other. The benzyl-methyl moieties served as precursors to cationic sites and were brominated using N-bromosuccinimide (NBS) and then quaternized with N,N,N',N'-tetramethyl-1,6-diaminohexane (TMHDA). Controlled bromination and quaternization at specific positions of the benzylmethy-containing fluorene— sulfone segments and isopropylidene—sulfone segments can be achieved. ~1H NMR spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography were used to characterize the as-synthesized copolymers. Distinct microphase separation in the as-prepared AEMs was observed using small-angle X-ray scattering and transmission electron microscopy. The AEM containing fluorene—sulfone segments (IEC = 1.89 meq-g ) showed higher ionic conductivity and methanol permeability than that containing isopropylidene—sulfone segments (IEC = 2.03 meq-g~(-1)). Moreover, the former showed better alkaline stability than the latter.