十字形液晶分子混合物系统的相变  

Phase transitions of binary mixtures of cross-like liquid crystal molecules

作　　者：朱玲玲[1] 刘红[1] 

机构地区：[1]南京师范大学物理科学与技术学院,江苏南京210023

出　　处：《液晶与显示》2015年第2期194-201,共8页Chinese Journal of Liquid Crystals and Displays

基　　金：江苏省科技厅项目(No.BK2009399)

摘　　要：研究了由2种十字形液晶分子构成的混合物系统。假设分子间的简单相互作用,运用平均场理论,得到混合物液晶在分子结构参数rA(A类液晶分子短、长棒比)和约化温度t平面内的相图。结果表明,相图存在一Landau点,系统经此点由各向同性相可直接进入双轴向列相。此点所对应的优化分子结构与A,B类分子结构、混合比有关。按等比例混合的棒状、圆盘状液晶分子系统即具有此优化分子结构。随着B类液晶分子短、长棒的比值rB增加,Landau点处的rA减少。对比混合物系统和相分离系统的自由能曲线,发现增加异种液晶分子间的相互作用强度,升高温度,缩小异种分子间的形状差异可使系统不发生相分离。A binary mixture of two different cross-like molecules is considered.Supposing a simple interaction model between molecules,and using mean field approximation,phase diagrams in the plane of molecular structure parameter rA（the length ratio of short and long rods of A type molecule）and reduced temperature t are obtained.The results show there exists a Landau point,through which the binary mixture can enter directly from isotropic phase to biaxial nematic phase.The optimal molecular structure at this point depends on the structures,the number ratio of A and B type molecules.Mixing rod-like and plate-like molecules with equal numbers will lead to this optimal structure.When rB,the length ratio of short and long rods of B type molecules increases,the rAvalue at Landau point decreases.Comparing the free energy curves corresponding to mixed system and phase separated system completely,it is found that by increasing the interaction strength between different types of molecules,increasing temperature,decreasing the structural difference between different molecules,the chance of phase separation will be reduced.

关 键 词：混合物 双轴向列相 相变 

分 类 号：O753.2[理学—晶体学]