可聚合离子液体液晶构筑碱性阴离子交换膜

Balancing the trade-off effects of conductivity versus swelling degree becomes especially challenging in the development of alkaline anion exchange membranes (AEMs). The construction of a highly ordered microphase separated morphology based on the difference in hydrophobic/hydrophilic properties of polymers has been demonstrated as one of the most promising strategies. However, the ordered alignment of ionic clusters within AEMs is still rather limited due to their structural distributions with polydispersity. In this project, nanostructured liquid-crystalline (LC) materials with highly ordered and well-defined ionic channels via the self-assembly of polymerizable ionic liquids (ILs) are proposed as a versatile strategy for efficient ion transportation. The introduction of molecularly ordered nanostructures of LCs will construct continuous pathways for hydroxide ion transportation via hopping mechanism, and the formed hydrophobic phase will synergistically restrict the membrane swelling. Firstly, appropriate cationic groups with ideal alkaline stability for polymerizable amphiphilic ILs will be synthesized and investigated based on the designability of ILs. Then facile methods to construct LC phases, especially bicontinuous cubic phases will be proposed. The purpose of this project is to explore the enhancement of ionic conductivity by the phase separation of LCs at the molecular level. We expect this project will provide a new perspective for the rational design of nanostructured AEMs.

如何平衡电导率与溶胀率的关系是碱性阴离子交换膜应用发展中极具挑战的科学问题。目前的一种有效策略是通过调控聚合物分子的亲疏水差异实现阴离子交换膜内部的微相分离。然而受限于聚合物分子量的多分散性，通过高分子结构变化构筑微观有序的离子传导通道依然非常困难。基于此，本项目拟通过可聚合离子液体自组装形成的液晶体系为阴离子交换膜中高效离子传导通道的构筑提供思路。液晶体系中双亲分子的有序排列可以为氢氧根的传导提供快速通道，同时疏水尾链相互交联可以有效抑制膜材料的溶胀。在本项目中，一方面，利用离子液体的可设计性，优化聚离子液体单体，尤其是阳离子的化学结构，以提高阴离子交换膜的碱稳定性。另一方面，探索两亲性可聚合离子液体构筑不同液晶相态，尤其是双连续立方液晶的简便方法。以期明确液晶微观结构与阴离子传导机制的关系以及对阴离子传导性能的调控，希望聚离子液体与液晶的有机结合能为高效阴离子交换膜提供新的设计思路。

离子液体参与构筑的液晶体系是胶体与界面化学中研究较为成熟的一个方向，但其应用发展仍十分有限。通过将离子液体优异的物化性质与液晶高度有序的微观结构紧密结合，能够为新型能源装置中高效离子传导通道的构筑和调控提供相应的理论和实践依据，有效地拓宽了离子液体及离子液体液晶的应用。基于此，本项目通过可聚合离子液体自组装形成的液晶构筑阴离子交换膜中高效离子传导通道，液晶体系中双亲分子的有序排列可以为氢氧根离子的传导提供快速通道。利用离子液体的可设计性，优化聚离子液体单体，探索两亲性可聚合离子液体构筑多种不同相态液晶，尤其是双连续立方液晶的简便方法。通过原位光聚合实现液晶结构的高效固化，制备保留有液晶微观结构的阴离子交换膜，并对其综合性能进行研究。该项目的顺利实施，不仅明确了液晶微观结构与阴离子传导机制的关系以及对阴离子传导性能的调控，聚离子液体与液晶的有机结合也为高效阴离子交换膜提供了新的设计思路。