Preparation and Properties of Poly(Vinyl Alcohol)-Based Anion-Exchange Membranes with Different Cross-Linked Structures

In this paper, three novel cross-linked anion-exchange membranes (AEMs) based on poly(vinyl alcohol) (PVA) were prepared and characterized. Uncross-linked piperidine-functionalized PVA-based AEMs (PVA-MP) were prepared by the ring-opening reaction of 2,3-epoxypropyl-1-methylpiperidinium chloride (EPMPAC) grafted to PVA. Then, PVA-MP was modified using terephthalaldehyde (TPA), quaternized bis-epoxy phenylene oxide (QBEPO), and quaternized 3-aminopropyltriethoxysilane (QAPTES), resulting in TPAx-PVA-MP, QBEPOy-PVA-MP, and QAPTESz-PVA-MP. Due to the effective cross-linked structure, the alkali stability and mechanical properties of the three cross-linked membranes were improved compared with those of PVA-MP, and the ionic conductivity retention of all cross-linked membranes reached more than 86% after immersion in 1 M KOH solution at 80 °C for 15 days. Meanwhile, the experiments showed that the cross-linked structure might hinder OH– transport and ion channel formation, which led to the lower ionic conductivity of the three cross-linked membranes compared to PVA-MP. The introduction of additional cationic functional groups into the QBEPO cross-linked membrane increased its ionic conductivity slightly more than that of PVA-MP only at a lower cross-linking degree.