Laboratorio de Propiedades Termofísicas, Departamento de Física Aplicada, Universidade de Santiago de Compostela, Spain.
J Phys Chem B. 2012 Dec 6;116(48):14159-70. doi: 10.1021/jp309532t. Epub 2012 Nov 20.
Using molecular dynamics simulations we have studied the structure of alkylsulfate-based ionic liquids: 1-ethyl-3-methylimidazolium n-alkylsulfate [C(2)C(1)im][C(n)SO(4)] (n = 2, 4, 6 and 8). The structure of the different ionic liquids have been interpreted taking into account radial and spatial distribution functions, and structure factors, that allowed us to characterize the morphology of the polar and nonpolar domains present in this family of liquids. The size of the nonpolar regions depends linearly on the anion alkyl chain length. Furthermore, properties of the surface of ionic liquids, such as surface tension, ordering, and charge and density profiles, were studied using molecular simulation. We were able to reproduce the experimental values of the surface tension with a maximum deviation of 10%, and it was possible to relate the values of the surface tension with the structure of the liquid-vacuum interfaces. Microscopic structural analysis of orientational ordering at the interface and density profiles along the direction normal to the interface suggest that the alkyl chains of the anions tend to protrude toward the vacuum, and the presence of the interface leads to a strong organization of the liquid phase in the region close to the interface, stronger when the side-chain length of the anions increases.
利用分子动力学模拟，我们研究了基于烷基硫酸盐的离子液体的结构：1-乙基-3-甲基咪唑鎓正烷基硫酸盐[C(2)C(1)im][C(n)SO(4)]（n = 2、4、6 和 8）。考虑到径向和空间分布函数以及结构因子，我们对不同离子液体的结构进行了解释，这使我们能够描述该系列液体中存在的极性和非极性域的形态。非极性区域的大小与阴离子烷基链长度呈线性关系。此外，我们还使用分子模拟研究了离子液体表面的性质，如表面张力、有序性、电荷和密度分布。我们能够以最大 10%的偏差重现实验测量的表面张力值，并且可以将表面张力的值与液体-真空界面的结构联系起来。界面处取向有序的微观结构分析以及垂直于界面方向的密度分布表明，阴离子的烷基链倾向于伸向真空，界面的存在导致靠近界面的液相强烈组织化，当阴离子的侧链长度增加时，这种组织化更为强烈。
