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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Molecular Dynamics Modeling of Proton Transport in Nafion and Hyflon Nanostructures
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Molecular Dynamics Modeling of Proton Transport in Nafion and Hyflon Nanostructures

机译：Nafion和Hyflon纳米结构中质子传输的分子动力学建模

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摘要

Classical molecular dynamics modeling studies at 363 K are reported of the local atomic-level and macroscopic nanostructures of two well-known perfluorosulfonic acid proton exchange polymer membrane materials: Nafion and Hyflon. The influence of the different side-chain lengths in the two polymers on local structure is relatively small: Hyflon exhibits slightly greater sulfonate-group clustering, while Nafion has more isolated side chains with a higher degree of hydration around the SO3~- side-chain ends. This results in shorter mean residence times for water molecules around the end groups in Nafion. Hyflon also displays a lower degree of phase separation than Nafion. The velocities of the water molecules and hydronium ions are seen to increase steadily from the polymer backbone/water interface toward the center of the water channels. Because of its shorter side chains, the number of hydronium ions is ~50% higher at the center of the water channels in Hyflon, and their velocities are ~ 10% higher. The water and H3O~+ diffusion coefficients are therefore higher in the shorter side-chain Hyflon system: 6.5 × 10~(-6) cm~2/s and 25.2 × 10~(-6) cm~2/s, respectively; the corresponding values for Nafion are 6.1 × 10~(-6) cm~2/s and 21.3 × 10~(-6) cm~2/s, respectively. These calculated values compare well with experiment: 4 × 10~(-6) cm~2/s for vehicular H3O~+ diffusion.
机译：报告了在363 K上进行的经典分子动力学建模研究，报告了两种著名的全氟磺酸质子交换聚合物膜材料：Nafion和Hyflon的局部原子级和宏观纳米结构。两种聚合物中不同侧链长度对局部结构的影响相对较小：Hyflon表现出稍大的磺酸盐基团簇，而Nafion具有更多的孤立侧链，且围绕SO3〜-侧链的水合度更高结束。这样可以缩短Nafion中端基周围水分子的平均停留时间。 Hyflon还显示出比Nafion低的相分离度。观察到水分子和水合氢离子的速度从聚合物主链/水界面向水通道中心稳步增加。由于其较短的侧链，Hyflon中水通道中心的水合氢离子数量增加了约50％，其速度也增加了约10％。因此，在较短的侧链Hyflon系统中，水和H3O〜+的扩散系数更高：分别为6.5×10〜（-6）cm〜2 / s和25.2×10〜（-6）cm〜2 / s。 Nafion的相应值分别为6.1×10〜（-6）cm〜2 / s和21.3×10〜（-6）cm〜2 / s。这些计算值与实验结果比较：车辆H3O〜+扩散为4×10〜（-6）cm〜2 / s。

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