Nanophase segregation of nonpolar solvents in smectic liquid crystals of bent-shape molecules.
Nanophase segregation of nonpolar solvents in smectic liquid crystals of bent-shape molecules.
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弯曲形状分子近晶液晶中非极性溶剂的纳米相分离。
DOI：
10.1103/physreve.66.031708
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
A. Jákli
中科院分区：
文献类型：
--
作者：
M. Y. Huang;A. M. Pedreira;O. G. Martins;A. M. Figueiredo Neto;A. Jákli
本文报道了一种含非极性溶剂正十六烷（HEX）的双核液晶4-氯-1，3-苯基双[4-（4-n-十四烷氧基苯基亚氨基甲基）苯甲酸酯]的混合物的电光、量热、X射线和介电性能的测量结果。据观察，HEX的加入压低各向同性近晶相转变温度，但结晶温度没有显着变化。相反，结晶相的织构改变，并且在足够高的HEX浓度（>20重量%）下，出现光学各向同性相。高于40wt%HEX浓度，中间相完全消失，并发生直接的各向同性固体到各向同性液体的转变。随着HEX浓度的增加，转变焓、层有序性和电极化的幅度减小。X射线研究表明，HEX分子填充在近晶层之间，导致层间距增加约3 A。层间距的增加在5wt%的HEX下饱和。观察到的相分离似乎是由于柔性HEX分子和液晶分子的刚性弯曲核之间的空间相互作用。
Electro-optical, calorimetric, x-ray, and dielectric measurements are reported on a mixture containing a bent-core liquid crystal 4-chloro-1,3-phenylinebis [4-(4-n-tetradecyloxyphenyliminomethyl) benzoate] mixed with the nonpolar solvent n-hexadecane (HEX). It is observed that the addition of HEX depresses the isotropic-to-smectic phase transition temperature, but the crystallization temperature does not change considerably. Instead, the texture of the crystalline phase changes and, at sufficiently high concentrations of HEX (>20 wt %), an optically isotropic phase appears. Above 40 wt % HEX concentrations, the mesophase completely disappears and a direct isotropic solid-to-isotropic liquid transition takes place. At increasing HEX concentration, the transition enthalpies, the layer ordering, and the magnitude of the electric polarization decrease. X-ray studies reveal that HEX molecules pack in between the smectic layers, resulting in an increase of the layer spacing by about 3 A. The increase of the layer spacing saturates at 5 wt % of HEX. The phase segregation observed seems to be due to steric interactions between the flexible HEX molecules and the rigid bent cores of the liquid crystal molecules.