Méndez-Morales Trinidad, Carrete Jesús, Rodríguez Julio R, Cabeza Óscar, Gallego Luis J, Russina Olga, Varela Luis M
Grupo de Nanomateriais e Materia Branda, Departamento de Física da Materia Condensada, Universidade de Santiago de Compostela, Campus Vida s/n E-15782, Santiago de Compostela, Spain.
Phys Chem Chem Phys. 2015 Feb 21;17(7):5298-307. doi: 10.1039/c4cp04668d.
The bulk structure of mixtures of two protic ionic liquids, propylammonium nitrate and butylammonium nitrate, with a salt with a common anion, is analyzed at room temperature by means of small angle X-ray scattering and classical molecular dynamics simulations. The study of several structural properties, such as density, radial distribution functions, spatial distribution functions, hydrogen bonds, coordination numbers and velocity autocorrelation functions, demonstrates that increasing the alkyl chain length of the alkylammonium cation results in more segregated, better defined polar and apolar domains, the latter having a larger size. This increase, ascribed to the erosion of the H-bond network in the ionic liquid polar regions as salt is added, is confirmed by means of small angle X-ray scattering measurements, which show a clear linear increase of the characteristic spatial sizes of the studied protic ionic liquids with salt concentration, similar to that previously reported for ethylammonium nitrate (J. Phys. Chem. B, 2014, 118, 761-770). In addition, larger ionic liquid cations lead to a lower degree of hydrogen bonding and to more sparsely packed three-dimensional structures, which are more easily perturbed by the addition of lithium salts.
在室温下，通过小角X射线散射和经典分子动力学模拟，对两种质子离子液体（丙基硝酸铵和丁基硝酸铵）与一种具有常见阴离子的盐的混合物的整体结构进行了分析。对密度、径向分布函数、空间分布函数、氢键、配位数和速度自相关函数等几种结构性质的研究表明，增加烷基铵阳离子的烷基链长度会导致更分离、定义更清晰的极性和非极性域，后者尺寸更大。通过小角X射线散射测量证实了这种增加，这归因于添加盐时离子液体极性区域中氢键网络的侵蚀，测量结果显示，所研究的质子离子液体的特征空间尺寸随盐浓度呈明显线性增加，这与之前报道的硝酸乙铵情况类似（《物理化学杂志B》，2014年，118卷，761 - 770页）。此外，更大的离子液体阳离子会导致氢键程度降低以及三维结构堆积更稀疏，这些结构更容易因添加锂盐而受到扰动。
