The Shackling Effect in Cyclic Azobenzene Liquid Crystal  

作　　者：Yang Xiao Chong He Zi-Fan Yang Er-Qiang Chen Huan-Jun Lu Xiao-Hong Li Ying-Feng Tu 

机构地区：[1]State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials,College of Chemistry,Chemical Engineering and Materials Science,Soochow University,Suzhou 215123,China [2]Beijing National Laboratory for Molecular Sciences,Key Laboratory of Polymer Chemistry and Physics of Ministry of Education,Center for Soft Matter Science and Engineering,College of Chemistry,Peking University,Beijing 100871,China [3]Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application,School of Physical Science and Technology,Suzhou University of Science and Technology,Suzhou 215009,China

出　　处：《Chinese Journal of Polymer Science》2022年第6期584-592,共9页高分子科学（英文版）

基　　金：The financial support from the National Natural Science Foundation of China(Nos.21774090 and 22071167);a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions were gratefully acknowledged.

摘　　要：We demonstrate here a novel method for the design of liquid crystals(LCs)via the cyclization of mesogens by flexible chains.For two azobenzene-4,4′-dicarboxylate derivatives,the cyclic dimer,cyclic bis(tetraethylene glycol azobenzene-4,4′-dicarboxylate)(CBTAD),shows LC properties with smectic A phase,while its linear counterpart,bis(2-(2′-hydroxyethyloxy))ethyl azobenzene-4,4′-dicarboxylate(BHAD),has no LC phase.The difference is ascribed to the shackling effect from the cyclic topology,which leads to the much smaller entropy change during phase transitions and increases the isotropic temperature greatly for cyclics.In addition,the trans-to-cis isomerization of azobenzene groups under UVlight is also limited in CBTAD.With the reversible isomerization of azobenzene groups,CBTAD showed interesting isothermal phase transition behaviors,where the LC phase disappeared upon photoirradiation of 365 nm UV-light,and recovered when the UV-light was off.Combined with the smectic LC nature,a novel UV-light tuned visible light regulator was designed,by simply placing CBTAD in two glass plates.The scattered phase of smectic LC was utilized as the“OFF”state for light passage,while the UV-light induced isotropic phase was utilized as the“ON”state.The shackling effect outlined here should be applicable for the design of cyclic LC oligomers/polymers with special properties.

关 键 词：AZOBENZENE CYCLIC Liquid crystals Isothermal phase transition 

分 类 号：TQ317[化学工程—高聚物工业] O753.2[理学—晶体学]