Fréedericksz transition studies of the smectic A and smectic C liquid crystalline phases. by Alison Findon

Cover of: Fréedericksz transition studies of the smectic A and smectic C liquid crystalline phases. | Alison Findon

Published by University of Manchester in Manchester .

Written in English

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Thesis (Ph.D.), - University of Manchester, Department of Physics.

Book details

ContributionsDepartment of Physics.
The Physical Object
Number of Pages227
ID Numbers
Open LibraryOL19175125M

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The smectic phases 36 are more highly ordered than the nematic phase and are characterized by partial translational ordering of the molecules into layers, in addition to orientational correlations.

The simplest smectic phase is the smectic A (SmA) phase, which is represented schematically in Figure in the nematic phase, the long axes of the molecules are oriented on average in the same. As already proved by X-ray observations, smectic X* is observed to be a tilted phase which is further established by optical tilt angle studies.

The molecular modeling of smectic C*, smectic X* and smectic Re-entrant C* is illustrated in Fig. From the molecular model it can be inferred that smectic C* is a tilted phase with book-shelf by: 5.

Drozd-Rzoska A., Rzoska S.J., Zioło J. () Nonlinear dielectric spectroscopy near smectic A-smectic C* transition in ferroelectric liquid crystal DOBAMBC. In: Rzoska S.J., Mazur V.A.

(eds) Soft Matter under Exogenic Impacts. NATO Science Series II: Mathematics, Physics and Chemistry, vol Springer, DordrechtCited by: 1.

We study in this paper the dynamics of molecules leading to the formation of nematic and smectic phases using a mobile 6-state Potts spin model with Monte Carlo simulation. Each Potts state represents a molecular orientation.

We show that, with the choice of an appropriate microscopic Hamiltonian describing the interaction between individual molecules modeled by 6-state Potts spins, we obtain Author: Aurélien Bailly-Reyre, Hung T. Diep. Extensions of a previously presented Landau-de Gennes type liquid crystalline phase transition model for the direct isotropic/smectic-A (lamellar) a phase transition to the direct isotropic.

liquid crystalline phases have only chain exhibits a first order smectic A to smectic C phase transition, which is confirmed with thermal analysis detecting a large enthalpy change of kJ.

); i.e., there are many different types of smectic phases. As for the nematic phase, the smectic phases can be identified by optical polarising microscopy (see Chapter 9). InGrandjean was studying (by microscopy) a sample of smectic liquid crystal (later classified as smectic A) which showed stepped edges, indicating that the smectic.

On heating, the smectic LC glass showed a glass transition (TgLC) of 81 °C, while the isotropic liquid glass showed a glass transition (Tgiso) of 93 °C and transformed to the smectic LC at °C. The corresponding heat capacity increases were and J mol-1 K-1 for the smectic LC glass and the isotropic liquid glass, respectively.

The McMillan theory of the smectic-A phase is extended to two dimensions. Its predictions, which strongly differ from those in three dimensions, are found to be in disagreement with the experiment on monolayers of the polymer PLA [poly(l-lactic acid)] at the air–water contrast to the latter, the theory predicts that the smectic A-phase does not melt into the isotropic phase but.

A high-resolution calorimetric study has been performed in the vicinity of the isotropic to smectic-A phase transition of smectic liquid crystalline elastomers. The transition is weakly first.

A detailed study into the synthesis and characterization of achiral nonsymmetric dimeric bidentate ligands formed by combining salicylaldimine and cyanobiphenyl rodlike anisometric segments through a flexible spacer (varying in its length and parity) and their Cu(II) and Pd(II) complexes is spacer parity greatly influences the phase behavior of ligands; notably, the dimers with.

Interest in the smectic liquid-crystalline state of matter received a substantial boost with the discovery by Meyer in the mids that a chiral smectic C (SmC*) phase exhibits a spontaneous.

A phenomenological model permitting a unified description of different types of smectic liquid crystalline phases including the hexatic-B phase has been developed.

The model describes five different liquid crystalline phases: nematic (N), smectic-A (SmA), smectic-C (SmC), hexatic-B (HexB) and smectic-E Fréedericksz transition studies of the smectic A and smectic C liquid crystalline phases.

book. On heating, the smectic LC glass showed a glass transition (TgLC) of 81 °C, while the isotropic liquid glass showed a glass transition (Tgiso) of 93 °C and transformed to the smectic LC at °C. The X-ray Studies of a Crystalline Structure of bis-(4-p-hexyloxybenzal)phenylenediamine and its Polymorphic Smectic Mesophases Structure and Symmetry of Smectic Liquid Crystals X-ray Diffraction from a Smectic a Liquid Crystal Electron Diffraction Study of Liquid.

X-ray scattering studies indicated that a transition from the Smectic B liquid crystalline structure to the isotropic state occurred at a temperature of 77°C. It has long been known that polymers containing fluorinated side chains can exhibit extremely low surface energies.

However, it has been theoretically shown that systems of simple hard rod-like particles and their mixtures give rise to various unexpected smectic phases along with the most common LC sequence of the nematic—smectic—columnar phases based on computer simulations only with an excluded volume interaction taken into consideration.

@article{osti_, title = {High-Resolution X-Ray Study of Nematic-Smectic-A And Smectic-A-Reentrant-Nematic Transitions in Liquid-Crystal-Aerosil Gels}, author = {Ramazanoglu, M and Larochelle, S and Garland, C W and Birgeneau, R J and }, abstractNote = {We have studied the effects of quenched random disorder created by dispersed aerosil nanoparticle gels on the nematic to smectic.

Originally published inthis book describes in detail various experimental techniques used in the study of liquid crystals. It will be indispensable for established workers in the field as well as students embarking on liquid crystal research. Each chapter in the book is dedicated to an important experimental technique used in the study and characterisation of liquid crystalline systems.

Other more ordered phases possess different degree of bond-orientational and positional orders within the smectic layers. A good description of these so-called hexatic and crystal smectic phases can be found in reference exotic calamitic phases with long-range bond-orientational and/or positional order are known with and without molecular tilt with respect to the layers.

A theoretical model is developed for treating molecular dynamics at the nematic–smectic‐A (N–S A) phase transition, which is frequently second order. This model is motivated by electron‐spin‐resonance (ESR) spin‐relaxation studies of molecular probes.

The critical dynamics of the hydrodynamic modes is described in accordance with dynamic scaling arguments of Brochard. 3 Structure: x-ray diVraction studies of liquid crystals 65 Satyendra Kumar Introduction 65 Types of x-ray scans 67 Experimental details 70 DiVraction patterns of liquid crystal phases 74 The power of mosaic scans 78 Hexatic and crystal smectic phases 82.

structure, in contrast to the biaxial inclined smectic C. a b c Figure 2. Structure of a layer of a smectic liquid crystal: a)sA; b)sB; c)sc. The SA modification occurs at the highest temperature among smectic phases: when heated, it passes into a nematic or a cholesteric mesophase, or else into an isotropic liquid.

An example of a liquid. The introduction of chirality, i.e., the lack of mirror symmetry, has a profound effect on liquid crystals, not only on the molecular scale but also on the supermolecular scale and phase.

I review these effects, which are related to the formation of supermolecular helicity, the occurrence of novel thermodynamic phases, as well as electro-optic effects which can only be observed in chiral.

Liquid Crystal Structure Factor, Extinction Rules for 2D Lattices; X-ray Structure Analysis of Liquid Crystal Phases, Golden Rule of Liquid Crystal Structure Analysis, Reciprocal Lattice Method for Discotic Phases of 2D-Rectangular, 2D-Hexagonal and 2D-Tetragonal Columnar Phases; Calamitic Phases of Smectic A, Smectic E and Smectic T Phases.

Liquid crystals, sometimes called mesophases, occupy the middle ground between crystalline solids and ordinary liquids with regard to symmetry, energy, and properties.

Not all molecules have liquid crystal phases. Water molecules, for example, melt directly from solid crystalline ice into liquid water.

Properties of Liquid Crystals; Nematic and Smectic Phases. Chiral phases; Contributors and Attributions; A true liquid is isotropic, meaning that its properties are uniform in all directions— the result of its molecules being in constant random lline solids, in contrast, are anisotropic; optical- and other properties such as thermal and electrical conductivity vary with direction.

Liquid crystals can be divided into thermotropic, lyotropic and metallotropic phases. Thermotropic and lyotropic liquid crystals consist mostly of organic molecules, although a few minerals are also tropic LCs exhibit a phase transition into the liquid-crystal phase as temperature is changed.

Lyotropic LCs exhibit phase transitions as a function of both temperature and. Curvature Defects in Smectic A and Canonic Liquid Crystals.- AC and DC Mechanical Response of Smectic Liquid Crystals.- Molecular Statistical Model for Twist Viscosity in Smectic C Liquid Crystals.- Dynamic Shear Properties near a Smectic A to Smectic B Phase Transition.- Convective Instabilities in Cholesteric Smectic A Liquid Crystals.- IV.

The second chapter is related to the theoretical description of liquid crystalline polymers, networks, and gels, which deals with subjects such as the formation of liquid crystallinity in the polymer system, the phase transition and phase diagram, the molecular weight.

Liquid crystals can be divided into two broad categories: thermotropic and lyotropic. Thermotropic liquid crystal phases are formed by pure mesogens.

Here phase transitions are a function of temperature and heat is either consumed or generated during the transition. Lyotropic liquid crystal phases arise from mesogens in a solvent. The smectic-C phase is different from the smectic-A phase in that the material is optically biaxial, and the molecular arrangement is such that the long axis is tilted away from the layer normal (see Fig.

In smectic-C* liquid crystals, as depicted in Figure 1.l2c, the director axis ñ is. The report shows the strong impact of fullerene C60 nanoparticles on phase transitions and complex dynamics of rod-like liquid crystal dodecylcyanobiphenyl (12CB), within the limit of small concentrations.

Studies were carried out using broadband dielectric spectroscopy (BDS) via the analysis of temperature dependences of the dielectric constant, the maximum of the primary loss curve, and. Ferroelectric liquid crystal, denoted as Ce3, possesses the cholesteric (N*) and the tilted ferroelectric smectic C* (SmC*) phases with phase transition temperatures as follows: Cr °C SmC* °C N* °C Iso.

Absence of the orthogonal smectic A* phase for this material caused definite difficulties while obtaining a homogeneous.

As a result, the liquid crystalline phase transitions (i.e., crystal → SmE → SmA → I) were pushed to higher temperatures. The knowledge gained in this study will help us further design and achieve the ferroelectric smectic C* phase in mesogen-free comb-like sulfonylated liquid crystalline polymers.

Jakli and A. Saupe, Method To Obtain Uniform Bookshelf Textures In Smectic C* Liquid Crystals (). Article [PDF] A.

Jakli and A. Saupe, "Spontaneous transition from chevron to striped texture of a planar smectic C* liquid crystal", Physical Review A, 45, No.8, (). Article [PDF] A new liquid crystalline, optical material-based Schiff base core with a near to room-temperature mesophase, (4-methoxybenzylideneamino)phenyl oleate (I), was prepared from a natural fatty acid derivative, and its physical and chemical properties investigated by experimental and theoretical approaches.

The molecular structure was confirmed by elemental analysis, FT-IR (Fourier-Transform. Further increase in the length of the chain completely destabilized the liquid crystalline behavior due to the disorder induced by the flexible unit in relation to the rigid one, so compounds 5d and 5e are non mesomorphic.

Compounds 6a–e show predominantly smectic phases. The siloxane molecule induction is helpful to the more regular smectic phase formation and smectic phase stabilization, such as chiral S C (S C *) and S B phases. The siloxane molecule is helpful to reduce the phase transition temperature and broaden the liquid crystal temperature range of the S C * phase and, simultaneously, it will not induce.

Lubensky, T.C., and Chen, J.-C., Anisotropic critical properties of the de Gennes model for the nematic to smectic-A phase transition, Physical Review B 17, (). A series of flavones (n-F) substituted at the 4', and 6 positions was prepared, characterised by NMR (1H,13C), HRMS, and studied for liquid crystal properties.

The 4'-alkoxy,6-methoxyflavones (4-F–F) exhibit varying ranges of nematic and smectic A phases as evidenced by polarised optical microscopy and differential scanning calorimetry (DSC). Abstract. In this chapter, an introduction to the field of liquid crystals relevant to displays and devices is given.

It covers the structures of nematic, and smectic, calamitic liquid crystals that can be used as the switching elements in displays and nematic discotic and columnar nematic liquid crystals that can be used in optical films. The examinations enable us to give two systems of liquid crystalline phases.

The system based on the observation of the textures corresponds with the system based on the relations of miscibility.

All liquid crystalline phases investigated can be divided into four groups, one nematic, and three smectic; the latter being called A, B and C.

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