Drastic Phase Transition in Ionic Liquid [Dmim][Cl] Confined Between Graphite Walls: New Phase Formation

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• 作者：Maolin Sha^† ; ^‡ ; ; Guozhong Wu*^† ; ; Yusheng Liu^† ; ^‡ ; ; Zhongfeng Tang^† ; ^‡ ; ; Haiping Fang*^&#
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：March 19, 2009
• 年：2009
• 卷：113
• 期：11
• 页码：4618-4622
• 全文大小：243K
• 年卷期：v.113,no.11(March 19, 2009)
• ISSN：1932-7455

文摘

Confinement can induce unusual behavior in the properties of matter. Using atomistic molecular dynamics simulations, we report here a liquid-to-solid transition of a bilayer of ionic liquid 1,3-dimethylimidazolium chloride ([Dmim][Cl]) confined between graphite walls in order to mimic the phase transition of an ionic liquid confined to hydrophobic nanospace. It was found that the ionic liquid bilayer undergoes a clear and drastic phase transition at a wall distance of about 1.1 nm, forming a new high-melting-point solid phase with different hydrogen bonding networks. In the new phase, each cation is surrounded by the three nearest-neighbor anions, and each anion is also encircled by the three nearest-neighbor cations. Strong π−π stacking interactions are found between the cations of the bilayer solid. The anions can be formed into a hexagonal ring around the cations. The new bilayer solid is a high-melting-point crystal possessing a melting point of 825−850 K, which is higher than that of the bulk crystal by more than 400 K.