A Study of the Effect of Temperature on the Interfacial Properties of Liquid Crystal Films in the Presende of Competing Interactions (Materials Research)

与表面和界面相比，液晶膜中的分子排列在体积上是不同的。沉积在凹槽衬底上的LC薄膜在LC-空气界面和LC-衬底界面的对齐力之间存在竞争，这两种对齐力迫使分子垂直于表面排列，而LC-衬底界面的对齐力迫使分子平行于衬底平面排列。在以往对近晶A液晶膜的研究中，测量了一个临界厚度，超过该厚度时，来自凹槽界面的远程对准力占主导地位，而不是由空气- lc界面施加的短程对准力。厚度有一个范围，跨度约为10um，在这个范围内，短程和远程对齐力之间的竞争最为明显。对准力是导致许多过渡前现象以及薄膜内部表面记忆效应的原因。在这个项目中，将研究smA液滴临界厚度以上的不稳定区域作为温度的函数，以确定短程和远程对准力之间的相互作用。将注意lc -固体基板界面上方的区域。互动活动包括以下内容：(1)在肯特州立大学教授液晶物理性质的研究生课程，该课程是化学物理跨学科项目的一部分；(2)组织面向高中生和大学一、二年级学生的拓展活动。第二项活动将包括访问地区学校以及制作示范包。一个主要的目标是传达液晶研究和一般科学的跨学科性质。

The molecular arrangement in a liquid crystal (LC) film differs in the bulk compared to surfaces and interfaces. An LC film deposited onto a grooved substrate experiences a competition between the aligning forces at the LC-air interface, which force the molecules to align normal to the surface, and aligning forces at the LC- substrate interface, which forces the molecules to align parallel to the plane of the substrate. In previous studies on smectic A liquid crystal films, a critical thickness was measured beyond which the long-range aligning forces from the groove interface dominate over the short-range aligning forces imposed by the air-LC interface. There is a range in thicknesses, which spans approximately 10um, where the competition between short-range and long-range aligning forces is most pronounced. The aligning forces are responsible for many pretransitional phenomena as well as surface memory effects inside the films. In this project, the unstable region just above the critical thickness in smA droplets will be studied as a function of temperature to ascertain the interplay between short and long range aligning forces. Attention will be paid to the region immediately above the LC-solid substrate interface. Interactive activities consist of the following: (1) teaching a graduate course in liquid crystal physical properties, taught as part of the Chemical Physics Interdisciplinary program at Kent State University; and (2) organizing outreach activities for high school students and first and second year college students. This second activity will include visits to area schools as well as the development of demonstration kits. A major goal is to convey the interdisciplinary nature of liquid crystal research and of science in general.