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Side-chain-type imidazolium-functionalized anion exchange membranes: The effects of additional hydrophobic side chains and their hydrophobicity

Author:
Wei, Haibing, Li, Yan, Wang, Sheng, Tao, Guoqing, Wang, Tie, Cheng, Sheng, Yang, Shanzhong, Ding, Yunsheng
Source:
Journal of membrane science 2019 v.579 pp. 219-229
ISSN:
0376-7388
Subject:
anion-exchange membranes, hydrophilicity, hydrophobicity, polymers, separation, water uptake
Abstract:
Ionic-conductive polymers with highly ordered, phase-separated structure are the promising materials used as anion exchange membranes (AEMs), thanks to their pronounced ion mobility. In this study, apart from imidazolium-functionalized hydrophilic pendants, additional octyl and perfluorooctyl-containing grafts were tethered to the polymer backbone and the resultant structure-morphology relationships were systemically investigated. The results revealed that the introduction of hydrophobic side chains as well as the corresponding hydrophobicity plays an important role in the formation of a phase-separated morphology in the membrane. AEMs containing perfluorooctyl-containing pendants (PPO-x-Imy8Fz) exhibited a pronounced microphase-separated morphology with ion clusters of about 2–5 nm size and a spacing of ∼6 nm, while the membranes with octyl pendants (PPO-x-Imy8Cz) or no additional hydrophobic side chains (PPO-x-Im) only showed indistinct or no phase separation. In addition, PPO-x-Imy8Fz AEMs showed better ion conductivity and suppressed water absorption, thereby exhibiting a good balance between water uptake and ion conductivity. The results of this study provide an efficient strategy to guide the architectural design of high-performance AEMs.
Agid:
6346407