Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea.
Center for Soft and Living Matter, Institute for Basic Science, Ulsan, Republic of Korea.
Phys Rev E. 2019 Jul;100(1-1):012702. doi: 10.1103/PhysRevE.100.012702.
We investigate how chiral dopants affect the chiral symmetry breaking of lyotropic chromonic liquid crystals (LCLCs) focusing on the double-twist (DT) director configurations in a cylindrical capillary. LCLCs of unusual elastic properties tend to exhibit chiral director configurations under confinement despite the absence of intrinsic chirality. The DT director configuration in a cylindrical cavity with a degenerate planar anchoring, resulting from the large saddle-splay-to-twist elastic modulus ratio, is a representative example. Here we start by reexamining the DT configuration of nematic disodium cromoglycate in a cylindrical capillary and estimate the ratio of saddle splay to bend modulus K_{24}/K_{3}=0.5±0.1. Additionally, we study the DT configurations of the chiral nematic LCLCs with chiral dopants. The DT configuration becomes homochiral when the dopant concentration surpasses the critical concentration. We characterize these chiral DT configurations and provide a theoretical model on their energetics. Finally, we observe how the enantiomeric excess of chiral dopants determines the director configuration when dopants of two different handednesses are mixed.
我们研究手性掺杂如何影响溶致液晶（LCLC）的手性对称破缺，重点研究圆柱形毛细管中的双重扭曲（DT）指向矢构型。尽管没有固有手性，但具有异常弹性特性的 LCLC 在受限条件下往往会表现出手性指向矢构型。具有退化平面锚定的圆柱形腔中的 DT 指向矢构型，由于大的鞍形展曲与扭曲弹性模量比，就是一个典型的例子。在这里，我们首先重新研究了圆柱形毛细管中向列型 disodium cromoglycate 的 DT 构型，并估计了鞍形展曲与弯曲模量的比值 K_{24}/K_{3}=0.5±0.1。此外，我们还研究了手性掺杂的手性向列型 LCLC 的 DT 构型。当掺杂剂浓度超过临界浓度时，DT 构型变为同手性。我们对这些手性 DT 构型进行了表征，并提供了一个关于其能量学的理论模型。最后，我们观察了当两种不同手性的掺杂剂混合时，手性掺杂剂的对映体过量如何决定指向矢构型。
