质子交换膜是直接甲醇燃料电池（DMFC）的核心部件，其性能直接决定着电池的性能。含氟磺酸型质子交换膜（Nafion膜），具有良好的质子导电率，但是其甲醇渗透率较高。层层组装聚电解质多层膜对Nafion膜表面改性，可以在一定程度上降低甲醇的渗透。由于组装层中阴离子（磺酸离子）和阳离子（铵根离子）间的静电作用，大部分磺酸基团参与了离子交联，只有少量剩余的自由磺酸能传导质子，由于组装膜中缺乏自由磺酸，因此，组装膜的质子导电性比较低。针对上述问题，本项目将利用不对称电荷的刚性聚电解质，采用层层组装的方法，通过提高组装膜中自由磺酸的含量来提高质子导电率，通过控制交联程度提高Nafion膜的阻醇性能。系统研究各种组装条件对组装膜性能的调控规律。制备出结构可控、性能优异的复合膜及膜电极材料；解决目前DMFC所遇到的关键问题，推动含氟磺酸膜尽早走向实用化。

The proton exchange membrane acts as the key component in a direct methanol fuel cell (DMFC), which directly determines the performance of the battery. Nafion membrane has good proton conductivity but high methanol permeability. A layer-by-layer (LBL) assembly of a polyelectrolyte multilayer to modify Nafion is an effective method to reduce the methanol cross-over. Due to the electrostatic interaction between the anionic (sulfonic acid ions) and cations (ammonium ion) in the assembly layer, most of the SO3H groups in the polymer are engaged in ionic crosslinking, only a few of the SO3H groups in the polymer are relaxed (free SO3H), which could virtually transfer protons in a DMFC. Due to the decrease of the free SO3H groups in the assembled layers, the ionic crosslinking of polycations and polyanions on a Nafion membrane usually results in lower proton conductivity. To overcome these issues, the LBL assembly of an unbalanced charged rigid polyampholyte multilayer to modify Nafion is propose in this project by enhancing the content of free sulfonic acids to improve the proton conductivity, and by controlling the degree of crosslinking of the LBL membrane to hinder alcohol permeability. We will do much study on a variety of assembly conditions to control the performance of the LBL membrane. Preparing the well controlled structure, the best performance of the composite membrane and membrane electrode material, resolving the key issues of the DMFC, to promote the fluorinated sulfonic acid membrane to practical use as soon as possible.