Remote-Controllable Molecular Knob in the Mesomorphic Helical Superstructures

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• 作者：Dae-Yoon Kim ; Sang-A Lee ; Minwook Park ; Yu-Jin Choi ; Won-Jin Yoon ; Jin Soo Kim ; Yeon-Tae Yu and Kwang-Un Jeong
• 刊名：Advanced Functional Materials
• 出版年：2016
• 出版时间：June 27, 2016
• 年：2016
• 卷：26
• 期：24
• 页码：4242-4251
• 全文大小：5919K
• ISSN：1616-3028

文摘

A programed light-responsive chiral liquid crystal (LC) containing four photochromic azobenzene moieties covalently connected to a central bicyclic chiral core (abbreviated as AZ₄ICD) is newly designed, precisely synthesized, and efficiently applied as a remote-controllable molecular knob for the optically tunable thin film. First of all, phase evolutions and ordered structures of AZ₄ICD are systematically investigated by a combination of thermal, microscopic, scattering, and simulation techniques. Wide-angle X-ray diffractions of oriented AZ₄ICD samples indicate that the AZ₄ICD molecule itself basically forms layer structures: one is a low-ordered chiral smectic A LC phase (SmA*) with 5.61 nm layer periodicity at high temperatures, and two highly ordered smectic crystal (SmCr₁ and SmCr₂) phases are subsequently formed at lower temperatures with the anticlinically tilted molecular packing structures. The helical superstructures of chiral nematic LC phase (N*) can be spontaneously constructed by doping AZ₄ICD chiral agents into the achiral nematic molecules. Due to the bent conformational geometry of AZ₄ICD, the thermal window of blue LC phase (BP) is expanded by stabilizing the double twisted cylindrical building blocks. Remote-controllable phase transformations in the mesomorphic helical superstructures are demonstrated by tuning the wavelength of light.