Molecular orientation of smectic liquid crystals between rigid substrates

Abstract

Self-assembling materials such as colloid, block copolymers, supramolecules and surfactants have been shown to be extremely versatile in the generation of functional structures. Recently, smectic liquid crystalline materials have been suggested as a new class of soft building blocks. The defect ordering of smectic LC self-assemblies takes advantage of the ability to achieve fast stabilization of molecular ordering and structure due to the reversible and noncovalent interactions of the LC molecules. We studied that the two types of liquid crystal defects, TFCDs and Zigzag pattern, can be controlled by several methods which are including surface treatment, micro-size confined system. The thesis consists of 3 chapters. At first, Chapter 1 of “Introduction” section briefly explain and overview about whole researches in this thesis. Chapter 2, 3 introduce the study of periodic smectic liquid crystal defect structures, such as toric focal conic domains (TFCDs) and optical zigzag pattern, within micro-size confined system. Chapter 2 shows the effect of surface hydrophilicity on the formation of FCD in Smectic liquid crystal. We present a study of FCDs in different hybrid cells possessing different surface anchoring properties resulted from various surface treatment materials to generate stable FCDs. Chapter 3 shows the effects of confined geometry on the pitch length of “zigzags” SmA defect structure. Previously, we presented the first experimental evidence of highly periodic liquid crystal patterns called “zigzags” under confined boundary constraints. We demonstrate that the formation of the ````zigzag```` is strongly influenced by the width and depth; the pitch length of the ````zigzag```` increases with increasing in the width or depth. The study of LC defect structures are investigated by convolution methods between various microscopic techniques - polarized optical microscope (POM), scanning electron microscope (SEM), and scattering methods - X-ray dif...