Velez Jose X, Zheng Zhaofei, Beller Daniel A, Serra Francesca
Johns Hopkins University, Dept. Physics and Astronomy, Baltimore, USA.
Soft Matter. 2021 Apr 14;17(14):3848-3854. doi: 10.1039/d0sm02040k. Epub 2021 Apr 6.
Spontaneous emergence of chirality is a pervasive theme in soft matter. We report a transient twist forming in achiral nematic liquid crystals confined to a capillary tube with square cross section. At the smectic-nematic phase transition, intertwined disclination line pairs are observed with both helical and kinked lozenge-like contours, configurations that we promote through capillary cross-section geometry and stabilize using fluorescent amphiphilic molecules. The observed texture is similar to that found in "exotic" materials such as chromonics, but it is here observed in common thermotropic nematics upon heating from the smectic into the nematic phase. Numerical modeling further reveals that the disclinations may possess winding characters that are intermediate between wedge and twist, and that vary along the defect contours. In our experiments, we utilize a phase transition to generate otherwise elusive defect structures in common liquid crystal materials.
手性的自发出现是软物质中一个普遍存在的主题。我们报道了在限制于具有方形横截面的毛细管中的非手性向列型液晶中形成的瞬态扭曲。在近晶 - 向列相变时，观察到相互缠绕的位错线对，其具有螺旋状和扭结的菱形轮廓，我们通过毛细管横截面几何形状促进这些构型的形成，并使用荧光两亲分子使其稳定。观察到的织构与在诸如发色团等“奇异”材料中发现的织构相似，但这里是在常见的热致液晶从近晶相加热到向列相时观察到的。数值模拟进一步揭示，位错可能具有介于楔形和扭曲之间的缠绕特征，并且沿着缺陷轮廓变化。在我们的实验中，我们利用相变在常见的液晶材料中产生原本难以捉摸的缺陷结构。
