星型嵌段共聚物基连通离子相筹质子交换膜及其传导性能

Proton Exchange Membrane Based on the Star Shaped Block Copolymer with Well Connected Ionic Domain and Conductivity

以八官能度倍半硅氧烷(BCP-POSS)为引发剂,用两步原子转移自由基聚合(ATRP)合成了以聚甲基丙烯酸甲酯-b-聚苯乙烯为臂的星型POSS-(PMMA-b-PS)8嵌段共聚物。用后磺化方法制备具有相同磺化度的磺化杂化高分子POSS-(PMMA-b-SPS)8,并用以制备了质子交换膜(PEM)。分析了在不同水合状态下两种PEM的传导率随着湿度的变化规律,发现在同样低水合状态下具有较长SPS链段的PEM其质子传导率较高;TGA分析结果表明,两种PEM都具有高温保水性能和高的初始热分解温度;用透射电子显微(TEM)和原子力显微镜(AFM)分析了不同嵌段比例PEM的微相结构,发现具有较长SPS链段的PEM有利于质子传导的两相连通的微相形貌;用低场核磁共振分析仪测定了自旋-自旋弛豫时间T2和不同共聚物低水合状态下链段分子运动特性,发现具有较长SPS链段的PEM有较狭长且连通性较好的微相分离形貌,显示出较高的质子自旋扩散系数,在低湿度环境下具有较高的质子传导率。

Star shaped block copolymer POSS-(PMMA- b- PS)8was synthesized by a two step process of atom transfer radical polymerization(ATRP) with eight functionalized polyhedral oligomeric silisesquioxane POSS-(Cl)8as core and poly(methyl methacrylate-b-polystyrene) as arm. The POSS-(PMMA-bPS)8was then sulfonation treated to produce hybrid polymer POSS-(PMMA- b- SPS)8, which was finally used as the polymer matrix for making proton exchange membranes(PEMs). The examination of conductivity as function of relative humidity for PEMs of high and low hydration status respectively indicated that with longer SPS block length exhibited higher proton conductivity for the PEMs of low hydration status with the same λ i.e. the number of water molecular coupled to sulfonic acid groups. TGA analysis showed that two kinds of PEM all exhibited higher water retention capacity and higher initial decomposition temperature. A well-connected ionic domains in PEM with longer SPS block could be observed by transmission electron microscopy(TEM) and atomic force microscopy(AFM). The features of molecules motion of chain segments and spins relaxation time T2 for the PEMs of low hydration status were analyzed by low field nuclear magnetic resonance, and it is found that the well connected ionic domains could be observed also in the PEMs with longer SPS block, which exhibited higher proton spin- diffusion coefficient,therewith higher proton conductivity by low relative humidity.