侧链含多季铵基团聚芳醚酮阴离子交换膜的制备与性能

Preparation and properties of anion exchange membranes based on multiple quaternary ammonium groups

成功合成了一个同时带有季铵基团和烷基溴的小分子(1-溴-6-(三甲基铵)己基溴化物),通过季铵化反应,将其接枝在三乙烯二胺季铵化的聚芳醚酮上,制备了带有柔性侧链且侧链上含有多季铵基团的聚芳醚酮(TQPAEK).利用溶液流延的方法,并经碱化处理制备得到OH~–型阴离子交换膜.通过改变起始聚合物的溴代度,可有效调控阴离子交换膜的离子交换容量,其范围在1.75～2.57meq/g.膜的溶胀度、吸水率与离子传导率均随着离子交换容量的增加而增大.该阴离子交换膜具有良好的热稳定性和机械性能,特别是柔性侧链的引入,显著地提高了聚合物膜的柔韧性,其断裂伸长率最高可达103.2%,拉伸强度仍在28MPa以上.引入多季铵化柔性侧链,有利于高局部离子基团的富集程度,在膜内形成了明显的相分离结构.80℃下最高离子电导率可达74.35mS/cm.这些结果表明多季铵化聚芳醚酮阴离子交换膜有望应用于燃料电池.

Anion exchange membrane fuel cell(AEMFC) has attracting great attention as one of the most clean energy conversion technologies, because it has a facile electrochemical kinetics under alkaline condition and enables the use of non-precious metal catalysts. The reported anion exchange membranes were usually prepared by tethering quaternary ammonium groups(QA) to the backbone of chloromethylated or bromomethylated aromatic polymers by immersing in trimethylamine solution. However, they exhibit much low ionic conductivity and poor alkaline stability, which hinders the further development of AEMFC technology. In order to improve the ionic conductivity of anion exchange membranes, we located multi QA groups on one side chains for enhancing the local density of ionic groups. Therefore, we synthesized a type of small molecule with a quaternary ammonium group and an alkyl bromide. After gethering it onto 1,4-diazabicyclo[2.2.2] octane-functionalized poly(arylene ether ketone) by a quaternization reaction, tri-quaternized poly(arylene ether ketone)(TQPAEK) was successfully prepared with flexible side chains containing multi quaternary ammonium groups. Then a series of anion exchange membranes in OH^-form were obtained by solution casting and then alkaline treatment. The ionic exchange capacity of these membranes in the range of 1.75–2.57 meq/g could be adjusted by controlling the degree of bromination of the precursor polymer. The water uptake, swelling ratio and hydroxide conductivity of TQPAEK membranes increased with the increasing IEC values. They also showed good thermal and mechanical stabilities. Especially, the introduction of flexible side chains significantly improved the elongation at the break of membranes, which reached up to 103.2%. Meanwhile, the tensile stress was still higher than 28 MPa. AFM images showed that the hydrophilic/hydrophobic phase-separation morphology was formed in these TQPAEK containing multi-quaternized flexible side chains. Therefore, TQPAEK exhibited high ionic conductivity of 74.35 mS/cm at 80°C. The results indicated that TQPAEK membranes had the potential to be used in alkaline AEMFCs.