Equilibrium morphology of tactoids in elastically anisotropic nematics
Equilibrium morphology of tactoids in elastically anisotropic nematics
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DOI：
10.1039/d2sm00323f
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发表时间：
2022-10-07
期刊：
影响因子：
3.4
通讯作者：
Vinals, Jorge
中科院分区：
文献类型：
--
作者：
Schimming, Cody D.;Vinals, Jorge
我们通过使用 Q 张量表示来研究向列液晶中的二维类晶团簇晶。使用 Q 上具有特征值约束的 Maier-Saupe 形式的体自由能以及 Q 中高达立方阶的弹性项来了解各向异性锚定和 Frank-Oseen 弹性对向列各向同性域形态的影响。此外，引入体积限制以稳定任何大小的类晶团聚体共存。我们发现，各向异性锚定会导致界面厚度的差异，具体取决于界面处指向矢的相对方向，并且当引入各向异性时，界面会变为双轴以实现切向对准。对于负类晶团簇，边界拓扑引起的表面缺陷随着弹性各向异性的增加而变得更加尖锐。另一方面，通过参数化研究它们的能量景观，我们发现表面缺陷并不代表正类晶团簇中的最小能量配置。相反，体中的 Frank-Oseen 弹性和各向异性锚定之间的相互作用产生了具有非圆形界面形态的半双极导向器配置。最后，我们发现，对于生长的类晶团簇，指向矢构型的演化对自由能中包含的各向异性项高度敏感，并且最小能量构型可能不能代表长时间动力学获得的类晶团簇。
We study two dimensional tactoids in nematic liquid crystals by using a Q-tensor representation. A bulk free energy of the Maier-Saupe form with eigenvalue constraints on Q, plus elastic terms up to cubic order in Q are used to understand the effects of anisotropic anchoring and Frank-Oseen elasticity on the morphology of nematic-isotropic domains. Further, a volume constraint is introduced to stabilize tactoids of any size at coexistence. We find that anisotropic anchoring results in differences in interface thickness depending on the relative orientation of the director at the interface, and that interfaces become biaxial for tangential alignment when anisotropy is introduced. For negative tactoids, surface defects induced by boundary topology become sharper with increasing elastic anisotropy. On the other hand, by parametrically studying their energy landscape, we find that surface defects do not represent the minimum energy configuration in positive tactoids. Instead, the interplay between Frank-Oseen elasticity in the bulk, and anisotropic anchoring yields semi-bipolar director configurations with non-circular interface morphology. Finally, we find that for growing tactoids the evolution of the director configuration is highly sensitive to the anisotropic term included in the free energy, and that minimum energy configurations may not be representative of kinetically obtained tactoids at long times.