CNR Institute on Membrane Technology, Unit of Padova, Via Marzolo, 1, 35131 Padova, Italy.
Phys Chem Chem Phys. 2019 Sep 18;21(36):20327-20337. doi: 10.1039/c9cp03296g.
We have investigated, by means of molecular dynamics simulations, the phase behaviour of mixtures of charged ellipsoidal Gay-Berne (GB) particles and spherical Lennard-Jones (LJ) particles, as a coarse-grained model of ionic liquid crystals (ILCs). The anisotropic GB particles represent cations usually found in ILCs, for example, pyridinium or bipyridinium salts, while the spherical LJ particles are taken as a model of anions like common halides, hexafluorophosphate and tetrafluoroborate. Here we have focused our attention on the effect of the stoichiometry of the system (that is, the GB : LJ ratio n : m in the salt formula [GB]n[LJ]m) on the stability and thermal range of the ionic liquid crystal phases formed, with special attention to the ionic nematic phase. To isolate the stoichiometry effect, a comparison of four different systems with GB : LJ ratios of 1 : 3, 1 : 2, 1 : 1 and 2 : 1 is made by keeping the packing fraction and the charge of the minor component fixed. Our results suggest a way to improve the stability of the ionic nematic phase by enhancing the anisotropic van der Waals interaction compared to the Coulomb interaction, and by increasing the proportion of anisotropic particles in the mixture.
我们通过分子动力学模拟研究了带电各向异性 Gay-Berne（GB）粒子和球形 Lennard-Jones（LJ）粒子混合物的相行为，作为离子液晶（ILC）的粗粒模型。各向异性的 GB 粒子代表通常在 ILC 中发现的阳离子，例如吡啶鎓或联吡啶鎓盐，而球形的 LJ 粒子则被用作阴离子的模型，例如常见的卤化物、六氟磷酸根和四氟硼酸根。在这里，我们关注的是系统化学计量的影响（即盐式[GB]n[LJ]m中的 GB:LJ 比 n:m）对形成的离子液晶相的稳定性和热范围的影响，特别关注离子向列相。为了隔离化学计量的影响，通过保持固定的堆积分数和小组分的电荷，比较了四个具有不同 GB:LJ 比（1:3、1:2、1:1 和 2:1）的系统。我们的结果表明，通过增强各向异性范德华相互作用相对于库仑相互作用，以及通过增加混合物中各向异性粒子的比例，可以提高离子向列相的稳定性。
