Structure and Dynamics of an Ionic Liquid Mixture Film Confined by Mica
Structure and Dynamics of an Ionic Liquid Mixture Film Confined by Mica
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DOI：
10.1021/acs.jpcc.9b05510
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发表时间：
2019-08-29
影响因子：
3.7
通讯作者：
Margulis, Claudio J.
中科院分区：
文献类型：
--
作者：
Karunaratne, Waruni V.;Margulis, Claudio J.
在最近的一篇文章（J. Phys. Chem. C 2019，123，4914-4925）中，我们使用分子动力学模拟研究了由1-甲基-3-辛基咪唑鎓辛基硫酸盐和1-乙基-3-甲基咪唑鎓乙基硫酸盐组成的离子液体（IL）混合物的结构，该混合物被真空界面限制。在这些界面处，混合物形成非极性阻挡层，将较小且极性更大的离子隐藏到液相的内部。在目前的工作中，对于相同的IL混合物，我们研究了（001）云母表面之间的限制的情况下，固体提供了一个平坦的和极性的离子界面。我们的重点是双重的;首先，我们想要了解在限制界面为高极性的边界处IL混合物的结构和动力学行为，其次，我们想要确定在离界面多远的地方恢复液体行为。这最后一点是特别重要的，根据令人费解的最近的实验结果的行为的离子液体和溶质溶解在他们的约束下，大的距离似乎是必要的恢复真正的散装行为。我们发现，IL混合物是高度结构化的吸附层，但在5 nm内批量样的结构特征被恢复。在我们的薄膜中心的动力学特性也出现收敛到散装行为，但需要进一步的研究，以充分解决的问题，在有限的IL膜的动力学。
In a recent article (J. Phys. Chem. C 2019, 123, 4914-4925) we studied using molecular dynamics simulations the structure of an ionic liquid (IL) mixture comprised of 1-methyl-3-octylimidazolium octylsulfate and 1-ethyl-3-methylimidazolium ethylsulfate confined by vacuum interfaces. At these interfaces, the mixture formed an apolar blocking layer concealing the smaller and more polar ions to the interior of the liquid phase. In the current work, and for the same IL mixture, we study the case of confinement between (001) mica surfaces, where the solid provides a flat and polar ionic interface. Our focus is twofold; first, we want to understand the structural and dynamical behaviors of the IL mixture at the boundary where the confining interface is highly polar, and second we want to establish how far away from the interface liquid behavior is recovered. This last point is particularly important in light of puzzling recent experimental results regarding the behavior of ILs and solutes dissolved in them under confinement, where large distances appear to be necessary to recover true bulk behavior. We find that the IL mixture is highly structured at the adlayer, but within 5 nm bulk-like structural features are recovered. Dynamical properties at the center of our thin film also appear converged to bulk behavior, but further studies are required to fully address the issue of dynamics within confined IL films.