Kim Jungmyung, Jeong Joonwoo
Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea.
Soft Matter. 2024 Feb 7;20(6):1361-1368. doi: 10.1039/d3sm01283b.
We study the chiral symmetry breaking and metastability of confined nematic lyotropic chromonic liquid crystals (LCLCs) with and without chiral dopants. The isotropic-nematic coexistence phase of the LCLC renders two confining geometries: sessile isotropic (I) droplets surrounded by the nematic (N) phase and sessile nematic droplets immersed in the isotropic background. In the achiral system with no dopants, LCLC's elastic anisotropy and topological defects induce a spontaneous twist deformation to lower the energetic penalty of splay deformation, resulting in spiral optical textures under crossed polarizers both in the I-in-N and N-in-I systems. While the achiral system exhibits both handednesses with an equal probability, a small amount of the chiral dopant breaks the balance. Notably, in contrast to the homochiral configuration of a chirally doped LCLC in the bulk, the spiral texture of the disfavored handedness appears with a finite probability both in the I-in-N and N-in-I systems. We propose director field models explaining how chiral symmetry breaking arises by the energetics and the opposite-twist configurations exist as meta-stable structures in the energy landscape. These findings help us create and control chiral structures using confined LCs with large elastic anisotropy.
我们研究了含有和不含手性掺杂剂的受限向列型溶致变色液晶(LCLC)的手性对称性破缺和亚稳性。LCLC的各向同性 - 向列共存相呈现出两种受限几何形状:被向列(N)相包围的无流动各向同性(I)液滴,以及浸没在各向同性背景中的无流动向列液滴。在没有掺杂剂的非手性系统中,LCLC的弹性各向异性和拓扑缺陷会引发自发扭曲变形,以降低展曲变形的能量代价,从而在I - in - N和N - in - I系统中,在正交偏振器下产生螺旋光学纹理。虽然非手性系统中两种旋向出现的概率相等,但少量的手性掺杂剂会打破这种平衡。值得注意的是,与本体中手性掺杂的LCLC的纯手性构型不同,在I - in - N和N - in - I系统中,不受欢迎旋向的螺旋纹理都有一定概率出现。我们提出了指向矢场模型,解释了手性对称性破缺是如何通过能量学产生的,以及相反扭曲构型如何作为能量景观中的亚稳结构存在。这些发现有助于我们利用具有大弹性各向异性的受限液晶来创建和控制手性结构。