光控取向引导的液晶序演变  

Photoalignment guided order evolution of liquid crystals

作　　者：罗道兴 吴金兵 郭政昊 胡伟[1] LUO Daoxing;WU Jinbing;GUO Zhenghao;HU Wei(College of Engineering and Applied Sciences,Nanjing University,Nanjing 210023,China)

机构地区：[1]南京大学现代工程与应用科学学院,江苏南京210023

出　　处：《液晶与显示》2024年第5期569-592,共24页Chinese Journal of Liquid Crystals and Displays

基　　金：国家重点研发计划(No.2022YFA1203703);国家自然科学基金(No.62035008)。

摘　　要：液晶独特的取向序和位置序为其带来奇特的物理性质,使其在凝聚态软物质中占据了重要的地位。由于液晶有序结构中连续对称性的破缺,引入了拓扑缺陷。而拓扑缺陷在相变过程中的转变机制及其在外场作用下的有序控制生成一直广受关注。通过控制液晶系统的空间尺度、边界条件和外场刺激,以及引入不同的热力学过程,液晶分子将呈现截然不同的组装行为,伴随各种拓扑缺陷的出现,以实现系统自由能的最小化。然而目前对液晶相变过程中拓扑缺陷的有序控制和动力学演变、外场作用下的受控转变行为和机制,以及拓扑缺陷应用探索等方面仍有待进一步研究。本文综述了本课题组利用光控取向技术实现高精度任意可编程的二维平面锚定设计,通过二维光取向层引导了液晶分子的三维排列,从而实现了不同相态下拓扑缺陷的可控有序大面积生成。进一步借助Landau-deGennes理论,揭示了拓扑缺陷在相变过程中的演化机制,并挖掘了其背后的演化规律。本研究丰富了人们对有序系统自组装行为的理解,为探索拓扑缺陷的可控生成及应用探索铺平了道路。Liquid crystals exhibit unique orientational and positional orders,granting them distinct physical properties that play a crucial role in the realm of condensed soft matter.The continuous symmetry breaking in ordered liquid crystal structures leads to the emergent of topological defects.The transformative mechanisms during phase transitions and ordered controlunder external fields have attracted intensive attentions.By manipulating the spatial scale,boundary conditions,and external field of the systems,liquid crystal molecules demonstrate diverse self-assembly behaviors during different thermodynamic processes,accompanied by the appearance of various topological defects,towards achieving the minimization of the system’s free energy.However,further exploration on the ordered control and dynamic evolution of topological defects during liquid crystal phase transitions,the controlled transition behaviors and mechanisms under external field,as well as the applications of topological defects is highly required.This review presents the latestworks conducted by our group,who utilizes photoalignment technique to achieve high-precision programmable two-dimensional planar anchoring designs.Through guiding the three-dimensional arrangement of liquid crystal molecules via a two-dimensional photoalignment layer,the controlled and ordered large-area topological defects under different phases are achieved successfully.Leveraging the Landau-de Gennes theory,the research discloses the mechanisms of topological defects during phase transitions and explores the underlying principles,significantly enriching our understanding on self-assembly of ordered systems and paving the way for applications of topological defects.

关 键 词：液晶 向列相 近晶相 Landau-deGennes理论 相变 拓扑缺陷 

分 类 号：O753.2[理学—晶体学]