具有相同核和永久偶极子相反取向的强极性分子组成的nematic liquid crystals二元混合物的研究
Studies on binary mixtures of nematic liquid crystals made of strongly polar molecules with identical cores and antagonistic orientation of permanent dipoles
摘要：
本文报道了两种双折射液晶（CCH-7和CCN-47）的光学（双折射）、介电（$Δn$）和弯曲-张开弹性各向异性（$ΔK=K_{33}-K_{11})$）的实验研究。特别地，连接到CCH-7的双环己烷核上的极性基团（-CN）沿纵向方向取向，而在CCN-47中，它沿横向方向取向。我们发现，除了显着的贡献的光学和介电各向异性，强极性基团的拮抗取向起着至关重要的作用，在确定弯曲-张开弹性各向异性。的弹性性能解释的基础上提出的模型，考虑到分子间的关联和由此产生的分子的长宽比的影响。
英文摘要：
We report experimental studies on optical (birefringence, $Δn$), dielectric $(Δ\varepsilon)$ and bend-splay elastic anisotropies ($ΔK=K_{33}-K_{11})$ of a few mixtures of two nematic liquid crystals, namely CCH-7 and CCN-47, made of highly polar molecules with identical cores and antagonistic orientation of permanent dipoles. In particular, the polar group (-CN) attached to the bicyclohexane core of CCH-7 is oriented along the longitudinal direction whereas, in CCN-47, it is oriented along the transverse direction. We show that apart from the significant contribution to the optical and dielectric anisotropies, the antagonistic orientation of strongly polar groups plays a crucial role in determining the bend-splay elastic anisotropy. The elastic properties are explained based on a model proposed by Priest, considering the effect of intermolecular association and the resulting length-to-width ratio of the molecules.
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