Solvent-induced self-assembly of uniform lying helix alignment of the cholesteric liquid crystal phase for the flexoelectro-optic effect
Solvent-induced self-assembly of uniform lying helix alignment of the cholesteric liquid crystal phase for the flexoelectro-optic effect
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DOI：
10.1080/02678292.2018.1425492
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发表时间：
2018-01
期刊：
影响因子：
2.2
通讯作者：
S. Bolis;C. Tartan;J. Beeckman;P. Kockaert;S. Elston;S. M. Morris
中科院分区：
文献类型：
--
作者：
S. Bolis;C. Tartan;J. Beeckman;P. Kockaert;S. Elston;S. M. Morris
摘要利用溶剂挥发技术获得了胆甾相液晶(LCS)的均匀平卧螺旋排列。溶剂挥发法允许自发形成几乎无缺陷的取向，即使在没有外部电场的情况下也是如此。少量的溶剂扩散到液晶中，并将其相转变为各向同性状态，在这种状态下，单个LC分子更具流动性。当溶剂扩散出LC并因此蒸发时，由溶剂提供的额外流动性允许分子达到最低能量构型，这取决于边界条件、溶剂挥发方向和分子间的弹性力。与剪切流诱导的取向相比，由于结构中的缺陷数量较少，溶剂诱导的ULH显示出亮态和暗态之间的对比度是前者的4倍多。通过对向列相LC E7的挠曲电光效应的测量，发现向列相LC E7的伸展和弯曲挠曲电系数之间的差值与文献报道的测量值(12.11.0pC/m)一致，表明溶剂自对准没有改变介质的电响应，但改善了其光学性质。图形摘要
ABSTRACT A uniform lying helix (ULH) alignment of cholesteric liquid crystals (LCs) is obtained using a solvent evaporation technique. The solvent evaporation method allows for the spontaneous formation of a virtually defect-free alignment, even in the absence of an external electric field. A small amount of solvent diffuses into the LC and changes its phase into isotropic state where the individual LC molecules are more mobile. As the solvent diffuses out of the LC and consequently evaporates, additional mobility provided by the solvent allows the molecules to reach the lowest energy configuration, dictated by the boundary conditions, the solvent evaporation direction and the elastic forces among the molecules. Compared to a shear-flow-induced alignment, the solvent-induced ULH exhibits a contrast ratio between the bright and dark states that is a factor of 4 times larger, due to the low number of defects in the structure. From measurements of the flexoelectro-optic effect, the difference between the splay and bend flexoelectric coefficients, , for the nematic LC E7 is found to be in agreement with the measured values reported in the literature (12.11.0 pC/m), demonstrating that the solvent self-aligning does not change the electric response of the medium, while improving its optical properties. GRAPHICAL ABSTRACT