Istituto per la Tecnologia delle Membrane del CNR (ITM-CNR), Sede Secondaria di Padova, Via Marzolo, 1-35131, Padova, Italy.
Soft Matter. 2017 Aug 2;13(30):5204-5213. doi: 10.1039/c7sm00612h.
We have investigated the effect of electrostatic interactions in mixtures of soft ellipsoids and spheres based on the well-known Gay-Berne (GB) and Lennard-Jones (LJ) potential, respectively. These model systems, in their original version, that is without any electrostatic charge, have been thoroughly investigated in the literature both as pure components and mixtures. In particular, mixtures of particles of different shapes, such as spheres and ellipsoids, tend to phase separate because of the excluded volume effects. Common ionic liquid crystals, based on imidazolium or other quaternary ammonium salts, are usually composed of roughly elongated (although flexible) cations and roughly spherical anions, that is, particles with a similar shape such as the GB and LJ models. Therefore, in this work, we present the results of molecular dynamics simulations of mixtures of positively charged GB and negatively charged LJ particles as models of ionic liquid crystals. Interestingly, by modulating the charge of the particles it is possible to stabilize isotropic, nematic, smectic and crystalline ionic phases. The relative weight of Coulomb (a radial, therefore isotropic interaction) and van der Waals (an anisotropic interaction) contributions is a key parameter to tune the stability of various mesophases.
我们研究了基于著名的 Gay-Berne（GB）和 Lennard-Jones（LJ）势的软椭球和球体混合物中的静电相互作用的影响。这些模型系统，在其原始版本中，即没有任何静电电荷，在文献中已经作为纯组分和混合物进行了彻底的研究。特别是不同形状的颗粒（如球体和椭球体）的混合物由于排斥体积效应往往会分相。常见的基于咪唑鎓或其他季铵盐的离子液晶通常由大致拉长（尽管灵活）的阳离子和大致球形的阴离子组成，即具有类似 GB 和 LJ 模型的颗粒。因此，在这项工作中，我们提出了带正电荷的 GB 和带负电荷的 LJ 粒子混合物的分子动力学模拟结果，作为离子液晶的模型。有趣的是，通过调节颗粒的电荷，可以稳定各向同性、向列、近晶和晶相离子相。库仑（径向，因此各向同性相互作用）和范德华（各向异性相互作用）贡献的相对权重是调节各种中间相稳定性的关键参数。
