State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
University of Science and Technology of China, Hefei 230026, China.
Soft Matter. 2023 May 24;19(20):3570-3579. doi: 10.1039/d2sm01706g.
The formation and transformation of defects in confined liquid crystals are fascinating fundamental problems in soft matter. Here, we use molecular dynamics (MD) simulations to study ellipsoidal liquid crystals (LCs) confined in a spherical cavity, which significantly affects the orientation and translation of LC molecules near the surface. The liquid-crystal droplet can present the isotropic to smectic-B phase transition through the smectic-A phase, as the number density of the LC molecules increases. We further find the change of LC structure from bipolar to watermelon-striped during the phase transition from smectic-A (SmA) to smectic-B (SmB) phases. Our results reveal the transition from bipolar defects to the inhomogeneous structures with the coexistence of nematic and smectic phases in smectic liquid-crystal droplets. We also study the influence of the sphere size in the range of 10 ≤ ≤ 50 on the structural inhomogeneities. It shows a weak dependence on the sphere size. We further focus on how the structures can be affected by the interaction strength . Interestingly, we find the watermelon-striped structure can be changed into a configuration with four defects at the vertices of a tetrahedron upon increasing the interaction strength. The liquid crystals at a strong interaction strength of = 10.0 show the two-dimensional nematic phase at the surface. We further present an explanation for the origin of the striped-pattern formation. Our results highlight the potential for using confinement to control these defects and their associated nanostructural heterogeneity.
受限液晶中缺陷的形成和转变是软物质中一个引人入胜的基础问题。在这里，我们使用分子动力学（MD）模拟研究了受限在球形腔中的椭圆液晶（LC），这显著影响了 LC 分子在表面附近的取向和平移。随着 LC 分子数密度的增加，液晶液滴可以通过向列相到近晶 B 相的转变呈现各向同性到近晶 B 相。我们进一步发现，在从近晶 A（SmA）到近晶 B（SmB）相的转变过程中，LC 结构从双极向西瓜条纹状转变。我们的结果揭示了在近晶液晶液滴中，从双极缺陷到具有向列相和近晶相共存的不均匀结构的转变。我们还研究了在 10≤≤50 的范围内球半径对结构不均匀性的影响。结果表明，它对球半径的依赖性较弱。我们进一步关注结构如何受到相互作用强度的影响。有趣的是，我们发现随着相互作用强度的增加，西瓜条纹结构可以变成四面体顶点处有四个缺陷的构型。相互作用强度为 = 10.0 的强相互作用下的液晶在表面呈现二维向列相。我们进一步解释了条纹图案形成的原因。我们的结果强调了利用限制来控制这些缺陷及其相关的纳米结构异质性的潜力。
