摘要
光响应胆甾相液晶是一类在光刺激下通过改变液晶分子排列调控光学特性的智能“软”光子晶体材料,其分子自组装形成周期性螺旋结构,选择性地反射与自身螺旋方向相同的圆偏振光。近年来,利用光刺激诱导胆甾相液晶在左手螺旋和右手螺旋之间发生螺旋翻转的研究引起了广泛关注。胆甾相液晶的螺旋翻转能够改变反射光的圆偏振特性,有望拓展光子晶体材料在可调节滤光器、防伪与加密技术、圆偏振激光器、三维显示等领域的潜在应用。本综述重点关注光响应胆甾相液晶螺旋翻转的研究进展;总结了调控胆甾相液晶螺旋方向的两种主要策略:(1)直接引入螺旋性可逆转变的光响应手性分子开关,(2)利用光响应手性分子开关和与之螺旋性相反的手性掺杂剂之间的手性竞争;分析了分子空间构型转变对调控螺旋翻转程度的影响;并讨论了不同材料体系面临的挑战以及未来的发展方向。
Light⁃driven cholesteric liquid crystals are soft intelligent photonic crystal materials,which change their optical properties upon irradiation of light.The molecules are organized into helical superstructures to selectively reflect the circularly polarized light with the same handedness as the light⁃driven cholesteric liquid crystals.By modulating the helical superstructures with light stimuli,the wavelength or polarization of the selective reflection is tuned.Light⁃driven handedness inversion of helical superstructures in cholesteric liquid crystals is currently in the limelight.The inversion of handedness alters the chirality of the circularly polarized light,which has wide potential for applications in tunable filters,anti⁃counterfeiting technologies,circularly polarized lasers,and 3D displays.However,inducing the handedness inversion of cholesteric liquid crystal still remains a challenge because the energy barrier between the opposite twist sense is difficult to overcome.It is necessary to figure out the universal strategies for designing light⁃driven cholesteric liquid crystal systems with reversible handedness inversion.This review mainly focuses on the development of the light⁃driven cholesteric liquid crystals with handedness inversion.The reported strategies for controlling the handedness are summarized,including the handedness inversion induced by reverse molecular chirality upon photoirradiation and introduction of chiral conflict.The reverse molecular chirality in different chiral molecular switches with tetrahedral,planar,or axial chirality induced by azobenzene,dithienylethene,overcrowded alkene,or cyano⁃functionalized diarylethene is concluded.During the photoisomerization process,the changes of conjugation,geometry,and dipole moment are analyzed.The strategies to introduce chiral conflict in cholesteric liquid crystals are demonstrated,and the mechanism of chiral conflict to facilitate handedness inversion is explained.Most importantly,the existing challenges and opportunities toward the systems are discussed.
作者
刘晓珺
秦朗
俞燕蕾
Xiaojun Liu;Lang Qin;Yanlei Yu(Department of Materials Science,State Key Laboratory of Molecular Engineering of Polymers,Fudan University,Shanghai 200433,China;South China Academy of Advanced Optoelectronics,SCNU-TUE Joint Lab of Device Integrated Responsive Materials(DIRM),South China Normal University,Guangzhou 510006,China)
出处
《化学进展》
SCIE
CAS
CSCD
北大核心
2023年第2期247-262,共16页
Progress in Chemistry
基金
国家自然科学基金项目(No.52173110,51903053)资助。
关键词
胆甾相液晶
螺旋翻转
光响应手性分子开关
螺旋结构
光开关
cholesteric liquid crystals
handedness inversion
light⁃driven chiral switches
helical superstructures
photoswitches
