蓝相液晶逐层相变过程的表征与机理探究  

Characterization and mechanism investigation of layer-by-layer phase transition process in blue phase liquid crystals

作　　者：郑成林 孙莉 王京霞[1,2] 江雷 ZHENG Chenglin;SUN Li;WANG Jingxia;JIANG Lei(Key Laboratory of Bionic Materials and Interface Science,Technical Institute of Physics and Chemistry,Chinese Academy of Sciences,Beijing 100190,China;Future Technology Institute,University of Chinese Academy of Sciences,Beijing 101408,China)

机构地区：[1]中国科学院理化技术研究所仿生材料与界面科学重点实验室,北京100190 [2]中国科学院大学未来技术学院,北京101408

出　　处：《液晶与显示》2024年第12期1679-1688,共10页Chinese Journal of Liquid Crystals and Displays

基　　金：国家自然科学基金(No.52373001,No.51873221,No.52073292,No.51673207,No.51373183,No.21988102)。

摘　　要：蓝相液晶是一种自组装三维软光子晶体,在传感显示、信息加密防伪、光学器件等领域具有广泛的应用前景。然而,有关蓝相相变的研究并不充分。本文对温度区间宽达2.5℃的单畴蓝相Ⅱ(BPⅡ)到蓝相Ⅰ(BPⅠ)相变过程进行光学和结构表征,采用晶体成核生长理论阐明了各阶段相变行为的机理。BPⅡ和BPⅠ共存阶段(BPⅡ-BPⅠ)反射光谱的双峰和Kossel衍射图案中圆环和四弧的叠加表明了该阶段是BPⅡ和BPⅠ相态的层状堆叠。利用偏光显微镜和低压扫描电镜观察到了BPⅡ、BPⅡ-BPⅠ、BPⅠ三个阶段的层状生长结构,发现BPⅠ从BPⅡ的刃位错中成核并外延生长,其相变过程从液晶盒上部逐层转变至下部。在BPⅠ阶段,刃位错和螺旋位错移动并合并,使织构转变为同心圆环状。本研究对完善蓝相相变理论和指导制备大面积单畴蓝相都具有重要意义。Blue-phase liquid crystals are self-assembled three-dimensional soft photonic crystals with a wide range of applications in the fields of sensing and display,information encryption,anti-counterfeiting,and optical devices.However,the research on the blue-phase phase transition is not sufficient.In this paper,phase transition process was investigated for the single-domain BPⅡto BPⅠ(a wide temperature interval 2.5℃)based on optical and structural features,and the mechanism of phase transition behaviors at each stage was elucidated by using the crystal nucleation and growth theory.BPⅡ-BPⅠcoexistence stage was proved by the bimodal peaks of the reflectance spectra and the superposition of circles and quadruple arcs in the Kossel diffraction pattern,which indicated simple superposition of the BPⅡand BPⅠphase state.The lamellar growth structures of the BPⅡ,BPⅡ-BPⅠ,and BPⅠphases were observed using polarized light microscopy and low-voltage scanning electron microscopy.BPⅠwas found to nucleate and grow epitaxially from the edge dislocations of BPⅡ,and its phase transition process transformed layer by layer from top to bottom of the cell.The edge dislocations and screw dislocations moved and merged at the BPⅠstage,transforming the texture into a concentric ring.This study is of great significance both for enrich the theory of blue phase transition and guiding the preparation of large-area single-domain blue phases.

关 键 词：蓝相 相变 层状结构 晶体成核生长 位错 

分 类 号：O753.2[理学—晶体学]