Theory of a helicoidal cholesteric phase induced by an external field
Theory of a helicoidal cholesteric phase induced by an external field
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DOI：
10.1080/02678292.2016.1144810
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发表时间：
2016-01-01
期刊：
影响因子：
2.2
通讯作者：
Matsuyama, Akihiko
中科院分区：
文献类型：
--
作者：
Matsuyama, Akihiko
我们提出了一个平均场理论来描述手性向列相液晶(LC)与高分子链的混合物以及在平行于胆甾相(CH)相节轴的纵向外场存在下的纯手性向列相液晶分子的螺旋胆甾相。螺旋面CH相的自由能(CH(H))是作为通常的取向有序参数和CH(H)相的有序参数的函数得到的。随着外场强度的增加，CH相由CH(H)相转变为向列相(N)相。根据温度和外场强度的不同，我们发现了二阶N-CH(H)和CH(H)-CH相变，以及一阶偏振(PN)-N、PN-CH(H)和PN-CH相变。我们还预测了外场作用下柔性聚合物和CH-LC分子混合物中的相图。
We present a mean field theory to describe a helicoidal cholesteric phase for mixtures of a chiral nematic liquid crystal (LC) and a polymer chain as well as for pure chiral nematic LC molecules in the presence of a longitudinal external field parallel to the pitch axis of a cholesteric (Ch) phase. The free energy of the helicoidal Ch phase (Ch(H)) is derived as a function of a usual orientational order parameter and an order parameter of the Ch(H) phase. On increasing the strength of the external field, we find that the Ch phase changes to the nematic (N) phase through the Ch(H) phase. Depending on the temperature and the strength of the external field, we find the second-order N-Ch(H) and Ch(H)-Ch phase transitions and the first-order paranematic (pN)-N, pN-Ch(H) and pN-Ch phase transitions. We also predict phase diagrams in mixtures of a flexible polymer and a Ch LC molecule under the external field.[GRAPHICS].