Nayani Karthik, Chang Rui, Fu Jinxin, Ellis Perry W, Fernandez-Nieves Alberto, Park Jung Ok, Srinivasarao Mohan
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Nat Commun. 2015 Aug 19;6:8067. doi: 10.1038/ncomms9067.
The presumed ground state of a nematic fluid confined in a cylindrical geometry with planar anchoring corresponds to that of an axial configuration, wherein the director, free of deformations, is along the long axis of the cylinder. However, upon confinement of lyotropic chromonic liquid crystals in cylindrical geometries, here we uncover a surprising ground state corresponding to a doubly twisted director configuration. The stability of this ground state, which involves significant director deformations, can be rationalized by the saddle-splay contribution to the free energy. We show that sufficient anisotropy in the elastic constants drives the transition from a deformation-free ground state to a doubly twisted structure, and results in spontaneous symmetry breaking with equal probability for either handedness. Enabled by the twist angle measurements of the spontaneous twist, we determine the saddle-splay elastic constant for chromonic liquid crystals for the first time.
处于具有平面锚定的圆柱几何形状中的向列型流体的假定基态对应于轴向构型的基态，其中，无变形的指向矢沿着圆柱的长轴方向。然而，当溶致变色液晶被限制在圆柱几何形状中时，我们在此发现了一种令人惊讶的基态，它对应于双扭曲指向矢构型。这种基态的稳定性涉及显著的指向矢变形，可以通过鞍形展曲对自由能的贡献来解释。我们表明，弹性常数中足够的各向异性驱动了从无变形基态到双扭曲结构的转变，并导致了两种手性具有相等概率的自发对称性破缺。通过对自发扭曲的扭曲角测量，我们首次确定了变色液晶的鞍形展曲弹性常数。
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