直接甲醇燃料电池用磺化聚芳醚类质子交换膜及同质立体化试剂结构设计、合成及应用

Sulfonated poly(arylene ether)s possess low methanol permeability, excellent heat resistance and high mechanical strength. However, their poor oxidation stability, low dimensional stability, and poor interfacial compatibility of ionomer with proton exchange membranes (PEM) in membrane electrode assembly (MEA) hamper their application in direct membrane fuel cells (DMFC). In order to improve their oxidation stability and low dimensional stability, novel covalent-ionically cross-linked sulfonated poly(arylene ether)s are proposed in this project. Flexible tertiary amine groups are introduced as side chains by activating of sulfonated poly(arylene ether)s. Then quaternary ammonium cationic group can be formed by the reaction of tertiary amines of the polymer side chains with a polyhalide. Moreover, the effects of cross-linking methods on the morphology, oxidation and dimensional stability of the resulting membranes will also be systematically investigated to try to build a method of developing PEM with high oxidation stability. Homogeneous ionomers featured by identical chemical structure but different in molecular weight and degree of sulfonation are synthesized. Furthermore, the chemical cross-linking can happen not only at the internal of ionomers but the interface between ionomers and PEM during hot-pressing. Thus the oxidation stability and miscibility of ionomers with MEA can be greatly reinforced. The effect of polymer architecture and cross-linking degree on miscibility between ionomers and PEM will also be studied. The successful implementation of present project will provide a scientific basis and technical support for the application of sulfonated poly(arylene ether)s in DMFC.

磺化聚芳醚质子交换膜具有低甲醇渗透率、良好的热稳定性和机械性能，但耐氧化和尺寸稳定性差、膜与催化层界面相容性差，制约了其在直接甲醇燃料电池（DMFC）中的应用。本项目提出共价交联和离子交联相结合解决制约膜氧化及尺寸稳定性差的关键科学问题。拟从磺化聚芳醚出发，经活化引入叔胺官能团，利用侧链叔胺与多卤代物反应性进行共价和离子交联。重点研究交联方法对膜微观形貌、氧化及尺寸稳定性等的影响规律，发展高氧化稳定性质子交换膜的调控方法。同时通过对膜与立体化试剂进行聚合物同质化设计，使用化学组成相同、分子量与磺化度不同的立体化试剂，并在膜电极热压过程中实现催化层立体化试剂及其与膜的化学交联，显著提高界面相容性和立体化试剂的稳定性，阐明立体化试剂结构、交联度等对膜与催化层界面相容性的影响规律。本项目的实施将为磺化聚芳醚类材料在DMFC上的应用奠定科学基础和技术支撑。

本研究旨在制备出具有良好尺寸稳定性和氧化稳定性的磺化聚芳醚质子交换膜，掌握立体化试剂的制备方法和膜电极组装工艺，建立膜与电极催化层界面相容的调控方案。研究内容包括：（1）从磺化聚醚醚酮出发，用1,1'-羰基二咪唑对磺酸基团进行活化，并接入1-(3-氨丙基)咪唑，再与1,4-二(溴甲基)苯交联，最终形成咪唑接枝交联型磺化聚醚醚酮膜。通过共价交联，膜的氧化稳定性和尺寸稳定性大幅提升，甲醇渗透率下降；（2）发展了主链改性的磺化聚苯醚酮/氧化石墨烯复合质子交换膜原位交联方法。磺化聚苯醚酮的磺酸基团催化氧化石墨烯上的羧基与聚合物疏水片段上的苯环发生F-C酰基化反应。氧化石墨烯既能增加疏水片段的长程有序性，又能促进质子传输；（3）制备了可溶于醇/水低沸点溶剂，又可交联的磺化聚醚醚酮立体化试剂，避免在催化层制备过程中引入高沸点极性溶剂，同时在膜电极热压过程中实现原位交联，有效提高膜电极的性能。