基于空间立体构型的高性能噻吩类阴离子交换膜的制备与表征

A brominated thiophene derivative with special molecular structure is designed, and then is used to synthesize thiophene-contained polymers with π-electron conjugated effect and spatial structure. The polymer is further used for preparing anion exchange membranes (AEMs) with effective ion conductive channels. The special monomer molecular structure can make the polymer main chain to form a planar structure, and the polymer backbone and side chain form a dihedral angle. This structure is efficient at the formation of ion conductive channels..The microstructure and morphology of the AEMs are characterized via various techniques. The ionic conductivity, ionic exchange capacity, swelling and mechanical property are measured. The thermal stability and alkaline stability of the AEMs are examined. The interrelation among those influence factors and the dependence of composition-microstructure-property of the AEMs are thus established. The microstructure of the AEMs and the diffusion mechanism of ions across the AEMs are studied by measuring the in-plane and through-plane diffusion coefficients of water and hydroxyl ions. The single cell is assembled, and hydrogen (methanol) is used as the fuel to test the electrochemical performance such as the voltage/current (power) density. The change in the single cell voltage with time at a constant current density is monitored. The chemical stability of AEMs in the working environment of alkaline fuel cells is evaluated. The research is expected to provide a guidance for the preparation of AEM with excellent stability and high performance.

设计具有特殊分子结构的溴化噻吩衍生物单体，进而合成具有π-共轭效应和空间立体结构的噻吩类聚合物，制备拥有良好离子传输通道的阴离子交换膜(AEM)。该单体分子结构能够使高分子主链形成平面结构，同时使高分子主链与侧链构成直角二面角，有利于形成高效的离子通道。研究膜的微观结构，探索聚合物空间立体结构对膜的溶胀性能、含水率、离子电导率、耐碱性、机械性能等影响。通过调节反应条件，构建适合阴离子传输的有效连续通道，建立膜的组成-微观结构-性能三者之间的内在联系，为制备性能优良的AEM提供理论指导。通过测试膜中水和氢氧根离子面内扩散系数和贯通面扩散系数，研究膜中离子传输机理。用膜制备电极材料，组装单电池，用氢气(甲醇)为燃料测试电压/电流(功率)密度等电化学性能。在一定电流密度下观察电压随时间变化，考察AEM在碱性燃料电池工作环境下的稳定性。研究可望对制备具有优异稳定性和高性能的AEM提供借鉴。

萘基具有片状结构，可以加强聚合物的空间折叠行为，进而促进阴离子交换膜(AEM)中亲疏水相的聚集，有效提升离子电导率。本项目着重探究萘基位于主链或侧链对AEM性能影响，主要进展如下：.萘基嵌段型AEM。通过Williamson反应和ATRP反应，制备了两种萘基三嵌段和双酚A三嵌段聚合物主链，通过溴化反应和Menschutkin反应，成功制备了两种不同类型的AEM。透射电镜、原子力显微镜和小角X光散射表征证实了相对于双酚A基嵌段AEM，萘基嵌段AEM有更明显的微相分离结构和较大的离子域，分子动力学模拟进一步证实了高效离子通道。80 oC时该种AEM(IEC=1.64 meq g-1)的离子电导率(103.05 mS cm-1)和单电池功率密度(160.73 mW cm-2)最高。80 oC时，相似IEC的萘基嵌段AEM比双酚A基AEM含水率(29.01%)及溶胀率(9.45%)更低，但离子电导率(59.40 mS cm-1) 更高和碱稳定性更好(离子电导率残留比为89.6%)。.萘基侧链型AEM。为进一步提升AEM的碱稳定性和机械性能，通过ATRP反应合成了全碳型主链，通过Williamson反应合成含萘基的长烷基链阳离子基团，进而制备了一种新型AEM。该种无吸电子基团主链AEM的碱稳定性极高，而长柔性侧链可以有效中和主链苯环的刚性，进而提升膜的机械性能。膜内存在明显的亲疏水相聚集行为和微相分离。80 oC时PSMS-NAPMQA-5膜(IEC=1.58 meq g-1)离子电导率为98.5 mS cm-1，单电池功率密度峰值为144.13 mW cm-2，2M NaOH处理1000 h后该种AEM (PSMS-NAPMQA-3)离子电导率残留率为93.5%。因此，可认为该结构AEM有应用于商业燃料电池的潜力。