由弹性键连接的V形分子双轴向列相液晶的相变  

Biaxial Nematic Liquid Crystal Phase Transition of V-Shaped Molecules Connected by Flexible Chain

作　　者：翟雪雅[1] 刘红[1] 

机构地区：[1]南京师范大学物理科学与技术学院,江苏南京210097

出　　处：《南京师大学报（自然科学版）》2010年第2期31-37,共7页Journal of Nanjing Normal University(Natural Science Edition)

基　　金：江苏省普通高校自然科学研究项目(07JKD140095)

摘　　要：对由弹性键相连的V形液晶分子系统的相变进行了研究.根据分子间简单相互作用能,利用平均场理论得到系统平衡态序参数随温度的变化,以及系统在分子结构和温度平面内的相图.结果表明液晶相变温度与弹性键强度系数k及棒长比r有关.当k>0和k<0且|k|<r时,随温度的降低,系统从各向同性相经一级相变进入单轴向列相;当k<0,r<1且|k|>时,系统由各向同性相经一级相变进入单轴相,再经二级相变进入双轴向列相,随着|k|的增大,一级相变消失,变为弱一级相变或连续相变.当k<0且|k|>r=1时,系统由各向同性相经一级相变进入双轴相,随着|k|的增大,一级相变消失,变为二级相变.The phase transitions in V-shaped molecular system where the two molecular arms are connected by a flexible chain are studied.Based on a simple interaction energy between molecules and the approximation of mean-field theory,order parameters of equilibrium state as functions of reduced temperature,and phase diagrams in the plane of molecular structure and temperature are obtained.The results show that the phase transition temperatures are related to the elastic strength of flexible chain k and ratio of two arms length r.When k〉0,or k〈0 but ｜k｜〈r,as the temperature decreases,system undergoes a first order transition from isotropic phase to uniaxial phase.When k〈0,r〈1 and ｜k｜〉r,system has a first order phase transition from isotropic to uniaxial phase,then a second order phase transition from uniaxial to biaxial phase.When ｜k｜ continues to increase,the first order will change into a weak first order or a continuous transition.When k〈0 and ｜k｜〉r=1,system has a first order phase transition from isotropic to biaxial phase.As ｜k｜ increases,the first order changes into a second order phase transition.

关 键 词：双轴向列相液晶 相变 弯曲核液晶 

分 类 号：O56[理学—原子与分子物理] O572.24[理学—物理]