聚合物近晶相有序结构固化构筑阴离子膜及其微相分离对电导率的提升机制

To solve the problem that the disordered structures of anion exchange membrane (AEM) for AEM fuel cells are harmful to the ion transfer, a novel idea is proposed, where AEM with ordered and interconnected ion channel will be prepared based on the ordered layer arrangement of liquid crystal polymers in smectic mesophase, which should be helpful to improve the hydroxide conductivity of AEM. The polystyrene and aromatic benzoheterocyclic derivatives with classical smectic mesophase will be chosen as main-chain and side-chain to prepare polystyrene-based side-chain liquid crystal polymers (SLCPs), respectively, and the structure-based adjustment factors for wide smectic mesophase range will be disclosed through investigating the correlations between the liquid crystal behavior and the main-chain/side-chain structures of SLCPs. Then the formation of the ordered ion channel will be achieved via shear orientation and fast solidification in smectic mesophase of SLCP, as well as quaternization and alkali treatment of the membrane for introducing the hydrophilic ionic groups, meanwhile, AEM will be built with ordered structures of hydrophobic/hydrophilic microphase separation. The effects of side-chain on the shape and structure of the ion channel will be investigated, and then the side-chain structure-based regulation for the construction of the interconnected ion channel will be revealed. Furthermore, the investigation on the performance of AEM, such as hydroxide conductivity and stability, as well as the characterization on the microstructure of AEM, will be carried out, and then the mechanism for promotion of the properties such as hydroxide conductivity and comprehensive performance resulted from the ordered microphase separation structures of AEM will be proposed. Series of AEMs with high performance will be developed according to the proposed method. We believe that, the project will show theoretical and application value not only for preparing AEM, but also for designing and preparing membranes with ordered structures.

针对燃料电池阴离子交换膜无序结构不利于离子传输的问题，本研究提出基于液晶近晶相层状结构，构筑有序、贯通性离子通道以实现膜电导率提升的新思路。拟采用具有典型近晶相的苯并杂环衍生物作为侧链，选择聚苯乙烯作为主链，通过亲核取代反应制备聚苯乙烯类侧链液晶聚合物，研究聚合物主、侧链结构与其液晶相行为的关联性，揭示宽近晶相区的聚合物结构调控因素；进而通过剪切取向和速冷固化聚合物的近晶相层状结构，采用季铵化和OH-交换引入亲水离子基团并形成有序离子通道，实现亲水/疏水区域有序微相分离膜的构筑，研究不同聚合物侧链结构对膜离子通道形状和结构的影响，揭示构建贯通性离子通道的侧链结构控制因素。继而考察膜电导率和稳定性等性能，表征膜微观结构，阐明有序性微相分离结构对膜电导率及其综合性能的提升机制，发展高性能膜材料。本研究不仅对构建阴离子膜具有理论和应用价值，而且对有序结构膜材料设计与制备具有重要指导意义。

燃料电池是一种清洁、高效、安全的绿色新能源，离子交换膜是聚合物电解质膜燃料电池的关键材料。针对离子交换膜无序结构不利于离子传输的问题，本研究提出基于液晶近晶相层状结构，构筑有序离子通道以实现膜电导率提升的新思路。.按照研究计划，首先设计并合成了含可离子化基团的苯并噁唑和苯并咪唑两个系列液晶化合物，揭示了苯并杂环化合物结构与其液晶相行为的关联性。其次设计并制备了含苯并杂环致晶单元侧链的聚苯乙烯、聚环氧氯丙烷、聚乙烯亚胺离子液晶聚合物，研究了侧链及离子基团对聚合物液晶相的影响规律。开发了系列新型侧链离子交换聚合物，考察了不同侧链、主链以及离子基团结构与离子交换聚合物膜力学性能、稳定性、电导率和单电池性能的关系。.研究结果发现，含苯并噁唑、苯并咪唑液晶基元侧链的聚环氧氯丙烷液晶离聚物，其σ/IEC达到了170以上，远高于商业Nafion117膜，是聚醚砜/聚醚酮类质子交换膜和阴离子交换膜σ/IEC的两倍和四倍。综合考虑氯/碘离子显著低于质子/氢氧根离子的迁移率，说明含苯并杂环致晶单元侧链的液晶离聚物，有助于构建有序离子通道以提升膜电导率，是潜在燃料电池用高性能膜电极材料。进一步研究发现侧链结构、聚合方式是膜微相分离结构形成与优化的关键因素之一，尤其是液晶有序结构有助于发展高电导率离子聚合物膜材料。此外，研究发现刚性芳香环与柔性烷基链共同组成的高密度离子化侧链结构，有助于获得高电导率σ、低甲醇渗透率PM和良好的尺寸稳定性，同时交联结构有助于显著提升离子交换膜的稳定性。例如，侧链型嵌段磺化聚醚砜B2SP和交联结构的CB2SP在80 oC时电导率分别为319和258 mS cm-1，单电池最大功率密度分别为2140 和1890 mW cm-2，远高于商用Nafion212（1350 mW cm-2），这主要归因于其高密度磺化侧链结构所带来的高σ、低PM和良好的尺寸稳定性。本研究结果对燃料电池用离子交换膜材料的设计与制备具有重要指导意义。