Sub-Nanometer Ion Channel Anion Exchange Membranes Having Rigid benzimidazole Structure for Selective Anion Separation
作者：Quan Chen, Yuyang Yao, Junbin Liao*, Junhua Li, Jingwen Xu, Tongtong Wang, Yuanyuan Tang, Yanqing X
關鍵字：selective anion separation, stiffness of polymer backbone, side-chain-type poly(arylene ether sulfone), anion exchange membrane, electrodialysis
論文來源：期刊
具體來源：ACS Nano
發表時間：2022年
Ion-conductive polymers having a well-defifined phase-separated structure show the potential application of separating mono- and bivalent ion separation. In this work, three side-chain-type poly(arylene ether sulfone)-based anion exchange membranes (AEMs) have been fabricated to investigate the effffect of the stiffffness of the polymer backbone within AEMs on the Cl?/NO3 ? and Cl?/ SO42? separation performance. Our investigations via small-angle X-ray scattering (SAXS), positron annihilation, and difffferential scanning calorimetry (DSC) demonstrate that the as-prepared AEM with a rigid benzimidazole structure in the backbone bears subnanometer ion channels resulting from the arrangement of the rigid polymer backbone. In particular, SAXS results demonstrate that the rigid benzimidazole-containing AEM in the wet state has an ion cluster size of 0.548 nm, which is smaller than that of an AEM with alkyl segments in the backbone (0.760 nm). Thus, in the electrodialysis (ED) process, the former exhibits a superior capacity of separating Cl?/SO42? ions relative to latter. Nevertheless, the benzimidazole-containing AEM shows an inability to separate the Cl?/NO3 ? ions, which is possibly due to the similar ion size of the two. The higher rotational energy barrier (4.3 × 10?3 Hartree) of benzimidazole units and the smaller polymer matrix free-volume (0.636%) in the AEM signifificantly contribute to the construction of smaller ion channels. As a result, it is believed that the rigid benzimidazole structure of this kind is a benefifit to the construction of stable subnanometer ion channels in the AEM that can selectively separate ions with different sizes.