The composite materials of acidic polymers and imidazole (Im) exhibit good high-proton conduction, making them potentially useful in proton-exchange membrane fuel cells. The proton conduction mechanism must be clearly elucidated for the design of future high proton-conduction materials. This study examines the local hydrogen-bonding structures and dynamics of Im for proton-conducting poly(vinylphosphonic acid)-Im (PVPA-xIm) composites by using molecular dynamics simulations. Radial distribution functions (RDFs) characterize the hydrogen bonds between Im or imidazolium cation (ImH⁺) and phosphonic acid (PA) groups and among Im molecules. RDFs and diffusion coefficients suggest that the intercalation of Im to PVPA reduces Im mobility because of the interaction between Im and PA groups. However, similar to pure Im, the amount of Im with fast rotational motions increases as the amount of Im increases. Our study leads us to conclude that long-range proton transport occurs through the hydrogen-bonding network of Im and that the fast rotational motions of Im enhance proton conduction in PVPA-xIm composites.

中文翻译：

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分子动力学研究聚（乙烯基膦酸）-咪唑复合物中咪唑分子的局部结构和动力学

酸性聚合物和咪唑（Im）的复合材料表现出良好的高质子传导性，使其潜在地可用于质子交换膜燃料电池。对于未来的高质子传导材料的设计，必须清楚地阐明质子传导机理。本研究通过分子动力学模拟研究了质子传导性聚（乙烯基膦酸）-Im（PVPA- x Im）复合材料的Im局部氢键结构和动力学。径向分布函数（RDF）表征Im或咪唑鎓阳离子（ImH ⁺）和膦酸（PA）基团以及Im分子之间。RDF和扩散系数表明，由于Im和PA基团之间的相互作用，Im插入PVPA会降低Im的迁移率。但是，类似于纯Im，随着Im量的增加，具有快速旋转运动的Im量也增加。我们的研究使我们得出结论，通过Im的氢键网络发生长距离质子传输，Im的快速旋转运动增强了PVPA- x Im复合材料中的质子传导。