纳米受限液晶的混杂基底锚定效应
Frustration of nanoconfined liquid crystals due to hybrid substrate anchoring
摘要：
我们提出了蒙特卡罗模拟的液晶材料限制在一个纳米级的狭缝孔。在等温条件下进行模拟，在一个专门的等应力合奏，其中N流体分子暴露于压缩应力作用在流体上的方向平行于基板平面。流体-流体和流体-基底相互作用的模型与我们以前的工作[M。Greschek等人，软物质，2010，DOI：10.1039/B 924417 D）。我们通过引入锚定函数（0<g（u）<1）来研究固体基底处的几种锚定机制，该锚定函数取决于流体分子相对于基底平面的取向; g（u）“切换”流体-基底吸引力的开启或关闭。在这里，我们专注于各种异构（即，混合）锚定方案在相对的衬底上施加不同的锚定功能。在我们以前的研究中，我们计算的等应力热容，使我们能够确定的状态，在该状态下的封闭流体进行结构转换。各向同性-非线性变换几乎与特定的锚定方案无关。这是因为在双相中的指向矢呈现的方向是在任一衬底处的竞争锚定方案所强制的方向之间的折衷。相反，在较低的压缩应力下，分子在特定方向上预排列，这取决于锚定方案的细节。
英文摘要：
We present Monte Carlo simulations of liquid-crystalline material confined to a nanoscopic slit-pore. The simulations are carried out under isothermal conditions in a specialized isostress ensemble in which N fluid molecules are exposed to a compressional stress acting on the fluid in directions parallel with the substrate planes. Fluid-fluid and fluid-substrate interactions are modelled as in our previous work [M. Greschek et al., Soft Matter, 2010, DOI:10.1039/B924417D). We study several anchoring mechanisms at the solid substrate by introducing an anchoring function (0<g(u)<1) that depends on the orientation of a fluid molecule relative to the substrate plane; g(u) "switches" the fluid-substrate attraction on or off. Here we focus on various heterogeneous (i.e., hybrid) anchoring scenarios imposing different anchoring functions at the opposite substrates. As in our previous study we compute the isostress heat capacity which allows us to identify states at which the confined fluid undergoes a structural transformation. The isotropic-nematic transformation turns out to be nearly independent of the specific anchoring scenario. This is because the director in the nematic phase assumes a direction that is a compromise between the directions enforced by the competing anchoring scenarios at either substrate. On the contrary, at lower compressional stresses molecules prealign in specific directions that depend on details of the anchoring scenario.
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