Origin of spontaneous polarization, tilt, and chiral structure of smectic liquid-crystal phases composed of bent-core molecules: A molecular model
Origin of spontaneous polarization, tilt, and chiral structure of smectic liquid-crystal phases composed of bent-core molecules: A molecular model
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DOI：
10.1103/physreve.70.021704
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发表时间：
2004-08-01
影响因子：
2.4
通讯作者：
Osipov, MA
中科院分区：
文献类型：
--
作者：
Emelyanenko, AV;Osipov, MA
提出了一个简单的分子模型，使人们能够解释实验观察到的手性结构的B2相组成的非手性香蕉形分子的起源新的非手性核心近晶相。结果表明，在完美有序的近晶相的香蕉形分子之间的分散相互作用稳定的自发极化，并可能是负责的指向矢倾斜。自发极化相对于倾斜平面的取向由色散和静电偶极-偶极分子间相互作用之间的平衡决定。特别地，足够强的偶极-偶极相互作用促进B2相，其中极化垂直于倾斜平面。B2相中的每个近晶层的实际手性结构是对称性破缺的结果。在小分子偶极子的情况下，形成非手性极性近晶相，其中自发极化平行于倾斜平面。开度角和香蕉形分子的轴比的作用也被认为是和相图。
A simple molecular model is proposed for novel bent-core smectic phases that enables one to explain the origin of the experimentally observed chiral structure of the B2 phase composed of nonchiral banana-shaped molecules. It is shown that in the perfectly ordered smectic phase the distributed dispersion interaction between banana-shaped molecules stabilizes the spontaneous polarization and may be responsible for the tilt of the director. The orientation of the spontaneous polarization with respect to the tilt plane is determined by the balance between the dispersion and electrostatic dipole-dipole intermolecular interactions. In particular, sufficiently strong dipole-dipole interaction promotes the B2 phase where the polarization is normal to the tilt plane. The actual chiral structure of each smectic layer in the B2 phase appears as a result of the symmetry breaking. In the case of small molecular dipoles the nonchiral polar smectic phase is formed where the spontaneous polarization is parallel to the tilt plane. The role of the opening angle and of the axial ratio of banana-shaped molecules is also considered and a phase diagram is presented.