Querciagrossa Lara, Ricci Matteo, Berardi Roberto, Zannoni Claudio
Department of Industrial Chemistry "Toso Montanari", University of Bologna, viale Risorgimento 4, 40136 Bologna, Italy.
Phys Chem Chem Phys. 2017 Jan 18;19(3):2383-2391. doi: 10.1039/c6cp05117k.
Extending the range of existence of biaxial nematic phases is key to their use in applications. Here, we have investigated using extensive molecular dynamics (MD) simulations of a coarse-grained model the possible advantages of using mesogenic mixtures. We have studied the phase organisation of five thermotropic mixtures of biaxial Gay-Berne (GB) ellipsoidal particles having the same volume, but different shapes and interactions, with aspect ratios ranging from rod-like to disc-like and, choosing fractional compositions so as to model a Gaussian dispersity of shapes. The parameterisation is based on a previous GB model with biaxialities of opposite sign for steric and attractive interactions which was shown to exhibit a stable biaxial nematic phase. We found that mixing different biaxial GB particles has an overall stabilising effect on the biaxial nematic phase with respect to temperature, layering and, to some extent also demixing. The mixtures show a decrease of ordering transition temperatures, a widening of nematic temperature ranges, and the formation of smectic phases at lower temperatures.
扩展双轴向列相的存在范围是其在应用中使用的关键。在此，我们使用粗粒化模型的广泛分子动力学（MD）模拟研究了使用介晶混合物的可能优势。我们研究了五种具有相同体积但形状和相互作用不同的双轴Gay-Berne（GB）椭球体粒子的热致混合物的相组织，其纵横比范围从棒状到盘状，并选择分数组成以模拟形状的高斯分散性。参数化基于先前的GB模型，该模型对空间位阻和吸引相互作用具有相反符号的双轴性，已显示出稳定的双轴向列相。我们发现，混合不同的双轴GB粒子对双轴向列相在温度、分层以及在某种程度上的相分离方面具有整体稳定作用。混合物显示有序转变温度降低、向列温度范围变宽，并且在较低温度下形成近晶相。
