高电导率稳定交联网络结构质子交换膜的制备及性能研究

Polymer electrolyte membranes (PEMs) are one of the key materials for fuel cell. Whereas how to solve the contradiction between a high proton conductivity and good stabilities is now the hot spot of development for PEMs and bottlenecks in PEM application. A novel idea is proposed according to the structure factor resulting to the contradiction, where PEMs with certain structure characteristics for high proton conductivity and network structure stabilized by multiple cooperative interactions will be constructed. Series of novel benzil monomers containing multiple active sites will be designed and synthesized. Series of crosslinkable side chain-type or main/side chain-type sulfonated polymer with high oxidative stability will be prepared via direct copolymerization of the monomers. A novel construction method for crosslinked PEMs stabilized by multiple cooperative interactions will be build up, where covalent/ionic/hydrogen bonding crosslinking structure will be formed via series reactions, such as cycle condensation of benzil group in side-chain, nuclei substitution of phenol groups, et al. The forming rule of the crosslinking structure will be discovered by measuring the structure of PEM prepared under different conditions. The correlation between the structure and properties of PEM will be revealed via studying the performances of PEM such as proton conductivity, stability, et al. The effection of cross-linked network structure on improving the performance of PEM will also be found. Cross-linked PEM with both high proton conductivity and high stability will be expected to be prepared,and a method for dissolving the the contradiction will be developed.We believe that,the development of design and preparation of PEM materials will be achieved, and the application of PEM will also be promoted through the project.

质子交换膜(PEM)是燃料电池的关键材料之一。PEM高电导率与其高稳定性之间的矛盾是目前PEM研究关注的热点和PEM应用的瓶颈。依据引起该矛盾的化学结构因素，本课题提出"在保持高电导率结构优势基础上，构建含多重交联网络结构的高稳定性PEM"策略。拟在合成结构新颖并含多活性位点的偶酰单体基础上，通过单体的缩聚反应，制备高抗氧化性可交联侧链或主/侧链复合磺化聚合物。进一步利用侧链偶酰基的缩环或酚羟基的亲核取代反应，制备含共价/离子/氢键等多重作用力协同交联网络结构的PEM；通过表征PEM结构，阐明交联结构随制膜条件变化的形成规律。研究PEM的电导率和稳定性等性质，揭示PEM结构与其性能的关系；阐明交联网络结构对于提升PEM性能的作用机理。期待制备的交联PEM在保持高电导率的同时具有高稳定性，解决PEM高电导率与其高稳定性之间的矛盾问题，实现PEM材料设计和制备技术的进步，促进PEM的应用研究。

质子交换膜(PEM)是燃料电池的关键材料之一。PEM高电导率与其高稳定性之间的矛盾是目前PEM研究关注的热点和 PEM应用研究的瓶颈。依据引起该矛盾的化学结构因素，本项目提出“在保持高电导率结构优势基础上，构建含多重交联网络结构的高稳定性 PEM”策略。在此基础上，设计合成了三种多活性位点的二氟芳香单体（DFDMED，DFTMP和AODFMED），通过缩聚反应制备了系列可交联侧链磺化聚合物。进一步利用侧链偶酰基的缩环反应，制备了含共价/离子/氢键等多重作用力协同交联网络结构PEM。研究结果发现，DFDMED基侧链磺化嵌段型聚醚砜表现出高的电导率（2.05 mequiv/g，80 oC时225 mS/cm）；DFTMP基侧链磺化聚醚砜虽然离子交换容量（IEC）较低（1.88 mequiv/g），但是其电导率较高（80 oC时208 mS/cm），归因于其高密度的磺化侧链结构。相应的交联膜表现出较低的吸水率、尺寸变化率、甲醇渗透率和较高的抗氧化稳定性，同时其电导率会有一定程度的下降。TEM研究表明，侧链和嵌段结构有利于亲水的磺化基团聚集构建离子通道，因而PEM电导率高；喹喔啉交联结构可以显著提高PEM的尺寸和化学稳定性，进而有助于实现PEM高电导率与高稳定性之间的平衡。在PEM研究的基础上，我们将相应的策略应用于阴离子交换膜（AEM）研制。设计合成了三种新型侧链结构二氟芳香单体（DFDB，DFDM和DFBDM），并制备了基于这三种单体的系列阴离子交换膜。通过引入了季铵盐和咪唑盐两种离子功能基团，研究了不同离子交换基团以及交联结构对膜性能的影响。研究结果发现，DFDM基侧链季铵盐嵌段型聚醚砜（1.15 mequiv/g）表现出优异的性能，其80 oC时电导率达到86.3 mS/cm，耐碱性较高。本项目研究结果为新型单体及高性能聚合物电解质膜材料的设计和开发提供了理论和技术支持。