[PDF] Chirality In Liquid Crystals From Bent Cores To Chromonics eBook

Author : Leah Elaine Bergquist
Publisher :
Page : 0 pages
File Size : 36,70 MB
Release : 2017
Category :
ISBN :

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Chirality is a central scientific concept but its superstructural and nanoscale manifestation are not well understood, severely limiting the potential of materials in a range of emerging applications. In the first part of this dissertation, we examine a lyotropic chromonic liquid crystal (LCLC) forming a nematic phase for its more intense response to gold nanoparticles capped with chiral L-cysteine ligand molecules than to their free molecular counterparts. We show that such nanoparticles induce a tighter chiral twist within, and similar among, the stacks of nematic LCLCs but with several orders of magnitude fewer chiral molecules. The second part of this dissertation focuses on the SmCP phase and the development of an optically isotropic antiferroelectric liquid crystal (OI-AFLC) display mode. This report describes in detail the synthesis and characterization of a series bent-core liquid crystal (LC) systems. Multi-component mixtures of these compounds achieved room temperature switching between optically isotropic and birefringent states; several mixtures displayed a modulated SmCaPA phase extending from below -40 °C up to about 100 °C. Requiring high fields and showing slow switching speeds, their utility is found in non-video-rate switching applications requiring high contrast.

Author : Peter J. Collings
Publisher : CRC Press
Page : 397 pages
File Size : 39,74 MB
Release : 2019-10-23
Category : Science
ISBN : 1351579827

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Introduction to Liquid Crystals: Chemistry and Physics, Second Edition relies on only introductory level chemistry and physics as the foundation for understanding liquid crystal science. Liquid crystals combine the material properties of solids with the flow properties of fluids. As such they have provided the foundation for a revolution in low-power, flat-panel display technology (LCDs). In this book, the essential elements of liquid crystal science are introduced and explained from the perspectives of both the chemist and physicist. This new edition relies on only introductory level physics and chemistry as the foundation for understanding liquid crystal science and is, therefore, ideal for students and recent graduates. Features Introduces and explains the essential elements of liquid crystal science, including discussion of how liquid crystals have been utilized for innovative and important applications. New to this edition are over 300 figures, 90 end-of chapter exercises, and an increased scope that includes recent developments. Combines the knowledge of two eminent scientists in the field; they have fully updated and expanded the text to cover undergraduate/graduate course work as well as current research in what is now a billion-dollar industry. Immerses the reader in the vocabulary, structures, data, and kinetic models, rapidly building up an understanding of the theories and models in current use. Begins with a historical account of the discovery of liquid crystals and continues with a description of how different phases are generated and how different molecular architectures affect liquid crystal properties.

Author : Heinz Kitzerow
Publisher : Springer Science & Business Media
Page : 513 pages
File Size : 48,86 MB
Release : 2006-04-28
Category : Science
ISBN : 0387216421

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Describes the main aspects of chirality in liquid crystals, and points out some of the open questions of current research. The chapters review the highlights of the important topics and questions.

Author : Hideo Takezoe
Publisher : CRC Press
Page : 290 pages
File Size : 41,78 MB
Release : 2017-07-20
Category : Science
ISBN : 1315355418

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Bent-Shaped Liquid Crystals: Structures and Physical Properties provides insight into the latest developments in the research on liquid crystals formed by bent-shaped mesogens. After a historical introduction, the expert authors discuss different kinds of mesophase structures formed by bent-shaped molecules. This book devotes the majority of its pages to physical properties such as polar switching, optics and non-linear optics, and behavior in restricted geometries. However, as chemistry is often highly relevant to the emergence of new phases, particularly with reflection symmetry breaking, it also involves a broad spectrum of interesting chemistry viewpoints.

Author : Quan Li
Publisher : John Wiley & Sons
Page : 598 pages
File Size : 17,30 MB
Release : 2012-05-29
Category : Technology & Engineering
ISBN : 1118078616

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The chemistry, physics, and applications of liquid crystals beyond LCDs Liquid Crystals (LCs) combine order and mobility on a molecular and supramolecular level. But while these remarkable states of matter are most commonly associated with visual display technologies, they have important applications for a variety of other fields as well. Liquid Crystals Beyond Displays: Chemistry, Physics, and Applications considers these, bringing together cutting-edge research from some of the most promising areas of LC science. Featuring contributions from respected researchers from around the globe, this edited volume emphasizes the chemistry, physics, and applications of LCs in areas such as photovoltaics, light-emitting diodes, filed-effect transistors, lasers, molecular motors, nanophotonics and biosensors. Specific chapters look at magnetic LCs, lyotropic chromonic LCs, LC-based chemical sensors, LCs in metamaterials, and much more. Introducing readers to the fundamentals of LC science through the use of illustrative examples, Liquid Crystals Beyond Displays covers not only the most recent research in the myriad areas in which LCs are being utilized, but also looks ahead, addressing potential future developments. Designed for physicists, chemists, engineers, and biologists working in academia or industry, as well as graduate students specializing in LC technology, this is the first book to consider LC applications across a wide range of fields.

Author : Kenneth Matthew Fergusson
Publisher :
Page : pages
File Size : 37,71 MB
Release : 2008
Category :
ISBN :

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The area of liquid crystals has received substantial research effort over the last century, particularly when the beneficial applications such as Liquid Crystal Displays (LCDs) were realised and developed. For the majority of this time, it has been considered that a linear molecular shape is required in order to generate a mesomorphic phase. It was therefore of particular interest and excitement when, in 1996, it was shown that a 'banana-shaped' molecular architecture could exhibit a new class of liquid crystalline phase. Additionally it was found that these new mesophases exhibited chiral domains, leading to electrooptical switching properties, despite the constituent molecules being achiral. Unsurprisingly, these observations have led to a vast frontier of research in the area of 'banana-shaped' and 'bentcore' systems over the past decade and many interesting properties relating to such systems have been reported. The work contained within this thesis investigates two areas of bent-core liquid crystals. Firstly, the introduction of fluoro-substituents to the bent-core of an achiral banana-shaped system has been assessed, in terms of both position, and number of substituents. The resultant mesomorphic properties of these compounds have shown that there is a very delicate boundary between banana, and 'conventional' mesomorphism, relating to subtle changes in molecular structure. Appropriately positioned fluoro-substituents upon the bent-core generate a more linear conformation, facilitating the generation of nematic phases. Possible reasoning for this observation has been discussed. Secondly, the effect of introducing a bent-core to a conventional calamitic structure, and the addition of fluoro-substituents, has been examined. Whilst a variation of this nature to the majority of calamitic molecular structures would have a severely detrimental effect upon the resultant mesophase morphology, it has been shown that this is not always the case and indeed the addition of fluoro-substituents is shown to enhance the mesomorphic stability of the smectic A phase.

Author : Clarissa Dietrich
Publisher : Cuvillier Verlag
Page : 190 pages
File Size : 49,94 MB
Release : 2019-12-09
Category : Science
ISBN : 3736961286

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Chirality is a phenomenon in nature that appears across all disciplines of natural science, from biology to mathematics. The spontaneous formation of chiral structures in a system of achiral components is known as spontaneous mirror symmetry breaking and is by itself of fundamental interest leading also towards the question of the origin of homochirality in nature in general. In this work, we show that by means of the topology imposed by the confining geometry and by interfacial boundary conditions – in combination with the physical properties of a liquid crystal – spontaneous mirror symmetry broken structures can be obtained. They are analyzed, inter alia, with respect to the types of geometrical confinements used, e.g. how the confinement amplifies, induces, and influences the detection of chirality effects in order to facilitate the measurement of tiny amounts of chiral additives qualitatively and quantitatively.

Author : Subas Dhakal
Publisher :
Page : 118 pages
File Size : 48,83 MB
Release : 2010
Category : Liquid crystals
ISBN :

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This dissertation addresses three distinct problems in liquid crystal: phase transitions among different SmCP phases of bent-core liquid crystal, flexoelectric effect in nematic liquid crystal and interplay between chirality and biaxiality in cholesteric liquid crystal. These problems are studied with computer simulations and analytical calculations. The first part of this dissertation is about chiral switching in smectic phases of bent-core liquid crystals. The phenomenon is investigated with a lattice Monte Carlo simulation and a phenomenological theory. Both methods show that the antiferroelectric (AFE) ground state switches into a ferroelectric state (FE) at sufficiently large electric field. In this transition, the chirality of the phase could change or not. In the case of weak inter-layer chiral coupling, anticlinic order of molecules from layer to layer could remain through the transition -thus changing the chirality of the phase. However, for a large value of chiral coupling, the anticlinic state could change to a synclinic state in the transition -thus preserving the chirality of the phase. Another area of focus is on flexoelectric effect in nematic liquid crystal. Recent experiments have shown that bent-core liquid crystals have a surprisingly large bend flexoelectric coefficient, up to 35 nC/m, roughly three orders of magnitude larger than the typical value. With this large bend flexoelectric coefficient, bent-core liquid crystals may be practical materials for converting mechanical into electrical energy. One of the focal points of this dissertation is to explain the large flexoelectric effect found in bent-core liquid crystals. Theoretical models of splay and bend flexoelectric effect are developed that incorporates the coupling between the director distortion (either splay or bend) and polarization. Through these models the flexoelectric response as a function of interaction parameters, temperature, and applied electric field is studied. Simulations and analytical calculations show that there is a large flexoelectric effect in the nematic phase, which diverges as the system approaches the transition to the polar phase. This observation demonstrated that flexoelectricity is not just a molecular effect but could be a statistical phenomenon associated with the response of correlated volumes of molecules, which increases as one approaches the polar phase. Finally, we investigate the statistical mechanics of chirality and biaxiality in liquid crystals through a variety of theoretical approaches, including Monte Carlo simulations, lattice mean-field theory, and Landau theory. All of these calculations show that there is an important interaction between cholesteric twist and biaxial order: The twist acts as a field on the biaxial order, and conversely, the biaxial order increases the twist, i.e. reduces the pitch. We model the behavior of chiral biaxial liquid crystals as a function of temperature, and discuss how the predictions can be tested in experiments.

Author : Hideo Takezoe
Publisher : CRC Press
Page : 0 pages
File Size : 13,8 MB
Release : 2015-12-26
Category : Science
ISBN : 9781482247596

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This book provides insight into the latest developments in the research on liquid crystals formed by bent-core mesogens. After a short historical introduction, the authors discuss different kinds of mesophase structures formed by bent-core molecules. A majority of this book is devoted to physical properties such as elasticity, optics and non-linear optics, and behavior in restricted geometries. As chemistry is often relevant to the emergence of new phases, particularly with chiral symmetry breaking, chemistry viewpoints are broadly involved in this book.

Author : Wei Lee
Publisher : Walter de Gruyter GmbH & Co KG
Page : 581 pages
File Size : 26,33 MB
Release : 2021-07-19
Category : Technology & Engineering
ISBN : 3110584379

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The work focuses on recent developments of the rapidly evolving field of Non-conventional Liquid Crystals. After a concise introduction it discusses the most promising research such as biosensing, elastomers, polymer films , photoresponsive properties and energy harvesting. Besides future applications it discusses as well potential frontiers in LC science and technology.