Nanostructural organization in ionic liquids
Nanostructural organization in ionic liquids
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DOI：
10.1021/jp056006y
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发表时间：
2006-02-23
影响因子：
3.3
通讯作者：
Pádua, AAH
中科院分区：
文献类型：
--
作者：
Lopes, JNAC;Pádua, AAH
使用分子模拟观察到室温离子液体中的纳米尺度结构。所研究的离子液体属于1-烷基-3-甲基咪唑类，阴离子分别为[C（n）mim][PF 6]和[C（n）mim][（CF 3SO 2）（2）N]。他们表示，第一次在模拟研究中侧重于远程结构，由AMBER/OPLS_AA家族的所有原子力场包含专门为这些化合物开发的参数。对于烷基侧链大于或等于C-4的离子液体，观察到非极性域中的烷基链的聚集。这些域渗透由阴离子和阳离子的咪唑环形成的离子通道的三维网络。纳米结构可以通过简单地对两种类型的结构域进行颜色编码而以明显的方式可视化（在这项工作中，我们选择红色=极性，绿色=非极性）。随着烷基链长度的增加，非极性结构域变得更大，连接更紧密，并导致离子网络溶胀，其方式类似于表现出微相分离的系统。这些纳米结构的功能上的离子液体的性能的后果进行了分析。
Nanometer-scale structuring in room-temperature ionic liquids is observed using molecular simulation. The ionic liquids studied belong to the 1-alkyl-3-methylimidazolium family with hexafluorophosphate or with bis(trifluoromethanesulfonyl)amide as the anions, [C(n)mim][PF6] or [C(n)mim][(CF3SO2)(2)N], respectively. They were represented, for the first time in a simulation study focusing on long-range structures, by an all-atom force field of the AMBER/OPLS_AA family containing parameters developed specifically for these compounds. For ionic liquids with alkyl side chains longer than or equal to C-4, aggregation of the alkyl chains in nonpolar domains is observed. These domains permeate a tridimensional network of ionic channels formed by anions and by the imidazolium rings of the cations. The nanostructures can be visualized in a conspicuous way simply by color coding the two types of domains (in this work, we chose red = polar and green = nonpolar). As the length of the alkyl chain increases, the nonpolar domains become larger and more connected and cause swelling of the ionic network, in a manner analogous to systems exhibiting microphase separation. The consequences of these nanostructural features on the properties of the ionic liquids are analyzed.