Structural Properties and Aggregation Behavior of 1-Hexyl-3-methylimidazolium Iodide in Aqueous Solutions

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• 作者：Paola D鈥橝ngelo ; Alessandra Serva ; Giuliana Aquilanti ; Sakura Pascarelli ; Valentina Migliorati
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：November 12, 2015
• 年：2015
• 卷：119
• 期：45
• 页码：14515-14526
• 全文大小：824K
• ISSN：1520-5207

文摘

The structural properties of 1-hexyl-3-methylimidazolium iodide ([C₆mim]I)/water mixtures with molar ratios ranging from 1:1 to 1:200 have been investigated using molecular dynamics (MD) simulations with extended X-ray absorption fine structure (EXAFS) experimental data. The presence of a complex network of interactions among cations, anions, and water molecules has been highlighted from the MD simulations, even if water molecules have been found to interact preferentially with the I^{鈥?/sup> anion. The EXAFS results show that, also for the 1:1 [C₆mim]I/water mixture, the water molecules are placed next to the I鈥?/sup> anion, and the I鈥?/sup> hydration shell becomes more and more crowded with increasing water content. Tight ion pairs have been detected in the [C₆mim]I/water mixtures with molar ratios from 1:1 to 1:12, while no ionic pairs were found in the most diluted solutions. The aggregation behavior has been determined from MD simulations with the aid of S(q) functions. For the most concentrated IL/water mixtures with molar ratios between 1:1 and 1:12 the existence of long-range structural correlations has been evidenced, even if the apolar chains are not completely segregated as expected for micelle-like structures. Conversely, for the 1:200 mixture, that is above the experimental critical aggregation concentration value, the alkyl chains are completely separated from each other.}