To T B T, Sluckin T J, Luckhurst G R
Mathematical Sciences, University of Southampton, Southampton, SO17 1BJ, UK.
Phys Chem Chem Phys. 2017 Nov 8;19(43):29321-29332. doi: 10.1039/c7cp04350c.
Liquid crystal dimers with odd spacers are good candidates as materials for biaxial nematic phases (N). The dimers are flexible molecules sustaining biaxial conformations, and couplings between the conformational and orientational distributions could be expected to stabilise N. We apply a molecular field theory for flexible molecules developed elsewhere to study a simple system made up of dimers composed of two cylindrically symmetric mesogenic groups. Our model allows for two idealised conformations: one linear and one bent at a tetrahedral angle. For a restricted set of chain lengths, the model predicts a first-order reentrant phase transition from the N phase into a low temperature uniaxial nematic phase (N). However the formation of the biaxial nematic could be blocked by the appearance of a twist-bent nematic.
具有奇数间隔基的液晶二聚体是双轴向列相（N）材料的良好候选者。这些二聚体是维持双轴构象的柔性分子，可以预期构象分布和取向分布之间的耦合会使N相稳定。我们应用在其他地方开发的用于柔性分子的分子场理论来研究一个由两个圆柱对称介晶基团组成的二聚体构成的简单系统。我们的模型允许两种理想化构象：一种是线性的，另一种是以四面体角度弯曲的。对于一组受限的链长，该模型预测从N相到低温单轴向列相（N）的一级折返相变。然而，双轴向列相的形成可能会被扭曲弯曲向列相的出现所阻止。
