Effect of the bis-imidazolium-based poly(ionic liquid) on the microstructure and the properties of AAEMs based on polyvinyl alcohol

A novel poly(ionic liquid) (PIL) based on bis-imidazolium is designed to improve the performances of alkaline nion exchange membrane (AAEM). As a result, the bis-imidazolium-based PILs AAEMs (PVA/DCnPIL) exhibit lower swelling ratio (higher dimensional stability) and higher chemical stability than that of mono-imidazolium-based PIL AAEM (PVA/C4PIL) under the same IEC value. Meanwhile, the length of the side chains of PILs was changed from the double imidazolium, which indueces a different microstructure that can affect the ionic conductivity and stability obviously. The SAXS results show that the PVA/DC8PIL can gnerate larger ionic clusters for facilitating the formation of interconnected broad ionic channels, which leads to higher conductivity in comparison with the PVA/DCnPIL (n = 4, 12) membranes. These observations unambiguously indicate that the designed bis-imidazolium-based PIL with an appropriate length of hydrophobic chains is an effective approach to increase the ion conductivity, dimensional and chemical stability of AAEMs.