RUI: Analysis of Phase Transitions, Biaxiality and Surface Effects in Chiral Smectic Liquid Crystals

California Polytechnic State University Foundation, San Luis Obispo CA

Investigators

Abstract

TECHNICAL SUMMARY This award supports theoretical research and education to investigate phase transitions between smectic structures in liquid crystals, specifically the smectic-A - smectic-C transition. Recently, there has been significant activity in the synthesis and experimental study of technologically promising new chiral liquid crystal materials. These materials exhibit Sm-A - Sm-C transitions with several unusual properties including very strong fluctuation effects, minimal layer contraction, and colossal electro-optical response, which is particularly appealing to the liquid crystal display (LCD) industry. The transition in most of the materials is either continuous and near a tricritical point, or first order. The central aim of this project is to study the chiral Sm-A - Sm-C transition. One focus of the research will be the transition at a tricritical point and the roles played by fluctuations and chirality. The project will also involve analysis of a novel chiral biaxial Sm-A phase, which may occur between the uniaxial Sm-A phase and the Sm-C phase. Biaxiality is a significant issue in the field of liquid crystals, particularly in the search for the elusive and technologically desirable biaxial nematic phase. Another component of the project will be the analysis of the surface electroclinic effect near a first order chiral Sm-A - Sm-C transition. The surface electroclinic effect is a phenomenon, of particular importance in the design of ferroelectric LCDs, whereby the chiral Sm-A - Sm-C transition can be locally induced near a surface. There is reason to believe that the surface electroclinic effect is particularly sensitive near the chiral first order Sm-A - Sm-C phase boundary. This project has both broad scientific and technological implications. It will further the fundamental understanding of phase transitions. Additionally, a theoretical framework for the properties of the unusual new materials discussed above will be technologically valuable in terms of optimizing their applications and guiding the future synthesis of desirable new materials. The wide-ranging applicability of liquid crystals in science and industry adds value to their study, particularly as the nation focuses increasingly on scientific and technological education and innovation. In particular, this award will support the training of undergraduate students in condensed matter and liquid crystals research. NON-TECHNICAL SUMMARY This award supports theoretical research and education on liquid crystals. Liquid crystals are a fascinating class of soft materials that have a rich variety of internal structures with molecules in spatial arrangements less organized than solid crystals but with directional patterns formed by the orientation of the constituent molecules. So, they can exhibit a range of phases intermediate between liquid and crystalline. These phases can be classified according to the types of order and patterning in their molecular arrangements. Liquid crystal materials exhibit transitions between different molecular arrangements or phases. An everyday example of a phase transition is between water and ice. The rich variety of liquid crystal order and phase transitions has led to considerable scientific interest in their properties. In addition to the fundamental scientific motivation to understand liquid crystals, there is significant technological incentive. Liquid crystals have many wide-ranging applications including LCDs, more explicitly liquid crystal displays, a multibillion dollar industry. This award will facilitate the investigation of a particular phase transition between layered structures in liquid crystals: the smectic-A - smectic-C transition. It will also allow the investigation of a possibly new phase, as well as the surface effects on liquid crystals. This last part of the project is important in the design of LCDs. This project has both broad scientific and technological implications. It will further the fundamental understanding of phase transitions. Additionally, a theoretical framework for the properties of the unusual new materials discussed above will be technologically valuable in terms of optimizing their applications and guiding the future synthesis of desirable new materials. The wide-ranging applicability of liquid crystals in science and industry adds value to their study, particularly as the nation focuses increasingly on scientific and technological education and innovation. In particular, this award will support the training of undergraduate students in condensed matter and liquid crystals research.