Liquid crystal effects on bacterial viability

The primary objective of this research was to test the hypothesis that lyotropic chromonic liquid crystals (neutral grey, red 14, blue 27, cromolyn) are not toxic to bacteria as compared with surfactant‐based lyotropic (CPCl and CsPFO) or thermotropic (5CB and E7) liquid crystals. Biocompatibility of most liquid crystals is currently unknown and is required for the development of systems interfacing liquid crystals and biological systems. Potential liquid crystal toxicity was evaluated by two methods. The first examined bacterial survival measured by bacterial growth over 24 hours, after exposure to various liquid crystals. The second toxicity method evaluated liquid crystal effects on bacterial membrane permeability using two fluorescent dyes. Three different types of bacteria were evaluated to assess bacterial structure differences with respect to liquid crystal toxicity. The results of this study indicate that lyotropic chromonic liquid crystals are not toxic to bacteria, whereas thermotropic and surfactant‐based lyotropic liquid crystals are toxic to one or more forms of bacteria. We conclude that lyotropic chromonic liquid crystals may be the preferred material in designing liquid crystal‐based systems that interact with biological systems, especially in the use of liquid crystal‐based biosensors.     

Active colloids in liquid crystals

Active colloids in liquid crystals (ACLCs) are an active matter with qualitatively new facets of behavior as compared to active matter that becomes isotropic when relaxed into an equilibrium state. We discuss two classes of ACLCs: (i) “externally driven ACLCs”, in which the motion of colloidal particles is powered by an externally applied electric field, and (ii) “internally driven ACLCs”, formed by self-propelled particles such as bacteria. The liquid crystal (LC) medium is of a thermotropic type in the first case and lyotropic (water based) in the second case. In the absence of external fields and self-propelled particles, the ACLCs are inactive, with the equilibrium LC state exhibiting long-range orientational order. The external electric field causes ACLCs of type (i) to experience translations, rotations, and orbiting, powered by mechanisms such as LC-enabled electrokinetics, Quincke rotations and entrapment at the defects of LC order. A dense system of Quincke rotators, orbiting along circularly shaped smectic defects, undergoes a transition into a collective coherent orbiting when their activity increases. An example of internally driven ACLCs of type (ii) is living liquid crystals, representing swimming bacteria placed in an otherwise passive lyotropic chromonic LC. The LC strongly affects many aspects of bacterial behavior, most notably by shaping their trajectories. As the concentration of bacteria and their activity increase, the orientational order of living liquid crystals experiences two-stage instability: first, the uniform steady equilibrium director is replaced with a periodic bend deformation, then, at higher activity, pairs of positive and negative disclinations nucleate, separate, and annihilate in dynamic patterns of topological turbulence. The ACLCs are contrasted to their isotropic counterparts.     

Narrowing of spontaneous emission and lasing in lyotropic and thermotropic liquid crystals

The narrowing of spontaneous emission and lasing are reported for the first time for a dye-doped lyotropic liquid crystal consisting of a methylbenzylamine solution of polybenzylglutamate (PBLG). Lasing was also studied in twisted nematics based on cholesterol derivatives. PBLG produces a cholesteric liquid crystal (CLC) with selective reflection in the visible region at PBLG concentrations above 55%. A comparison is made of the narrowing of spontaneous emission and lasing in lyotropic vs. thermotropic liquid crystals. In both cases lasing occurs where the selective reflection band overlaps the dye emission band. Thermotropic liquid crystals show a much lower lasing threshold than lyotropic systems. The lasing mechanism and the role of disorder in both systems are discussed.     

The distinction between chromonic and amphiphilic lyotropic mesophases

Optical microscopy, X-ray diffraction and NMR spectroscopy have been used to examine whether the hexagonal phases of representative chromonic and amphiphilic mesogens are miscible. The systems studied were octaoxyethylene-glycol dodecylether with either disodium cromoglycate or 5-n-hexyl-7-(5-methyl-sulphonimidoyl) xanthone-2-carboxylic acid. The results clearly demonstrate that the hexagonal phases of these two systems are not miscible, although miscibility does occur in the isotropic solution. These observations suggest that chromonic mesophases are a new breed of lyotropic liquid crystals.     

Freeze fracture TEM investigations in liquid crystals

This review describes the results obtained in the determination of the nanometric structures of liquid crystal systems using the technique of freeze fracture transmission electron microscopy (FF-TEM). I focus the review on two types of major results that were obtained with this technique in respectively lyotropic and thermotropic liquid crystals systems.     

Synthesis,characterization and recent developments of liquid crystalline polymers

Recent developments of polymer liquid crystals (PLCs) are reviewed. The virial expansion method of Onsager and the lattice model used by Flory to appreciate the most relevant parameters in establishing mesomorphic behavior in polymeric systems are presented. These and other theoretical predictions are confirmed by numerous experiments. Both lyotropic (polymer solutions) and thermotropic (polymer melts) types of PLCs are considered with emphasis placed on the latter. The general properties of mesophases formed by such polymers are surveyed and some chemical structures capable of producing mesophases are classified in relation to their ability to form lyotropic and thermotropic systems. The synthetic routes, the effects of polymer structure on physical properties, and applications of two major classes of lyotropic systems (polypeptides, polyamides) and of a range of potentially important thermotropic polymers are discussed.     

Planar and twisted lyotropic chromonic liquid crystal cells as optical compensators for twisted nematic displays

We have explored the use of lyotropic chromonic liquid crystals (LCLCs) as promising materials for optical compensators for liquid crystal displays. We used aqueous solutions of disodium cromoglycate in the range of concentrations that yield a chromonic N phase. The N phase is aligned by rubbed polyimide layers giving planar orientation. Two different types of LCLC-based elements are described: (a) a uniformly aligned planar N phase that forms an optically uniaxial plate with a negative birefringence; (b) twisted cells of LCLC obtained by doping the N phase with chiral amino acids. Both planar and twisted N* phase cells were used for compensation of the positive birefringence of twisted nematic (TN) displays; the TN devices were appreciably improved. We achieved achromatic dark state and contrast ratio up to 50:1 at all directions within a 40° cone of viewing angle.     

Planar and twisted lyotropic chromonic liquid crystal cells as optical compensators for twisted nematic displays

We have explored the use of lyotropic chromonic liquid crystals (LCLCs) as promising materials for optical compensators for liquid crystal displays. We used aqueous solutions of disodium cromoglycate in the range of concentrations that yield a chromonic N phase. The N phase is aligned by rubbed polyimide layers giving planar orientation. Two different types of LCLC-based elements are described: (a) a uniformly aligned planar N phase that forms an optically uniaxial plate with a negative birefringence; (b) twisted cells of LCLC obtained by doping the N phase with chiral amino acids. Both planar and twisted N* phase cells were used for compensation of the positive birefringence of twisted nematic (TN) displays; the TN devices were appreciably improved. We achieved achromatic dark state and contrast ratio up to 50:1 at all directions within a 40° cone of viewing angle.     

Organic lyotropic lamellar liquid crystals

X-ray diffraction experiments on smectic A and C forming thermotropic liquid crystals reveal that the smectic layer spacing increases with the addition of organic solvents to the host material. The rate of this increase indicates the formation of an organic lyotropic lamellar liquid crystal phase in which the solvent is intercalated between the smectic layers of the host liquid crystal.     

液晶润滑的研究进展*

综述了近10多年来国内外液晶润滑及液晶添加剂的研究进展。概括了溶致液晶和热致液晶的润滑性能的理论研究及实验结果, 比较了不同类型液晶的润滑机理及在不同实验条件下的抗减摩性能, 以及它们作为普通润滑剂、合成油脂等的添加剂时的润滑效果。     

Thermotropic liquid crystalline glycolipids

Are the liquid crystalline properties of the materials of living systems important in biological structures, functions, diseases and treatments? There is a growing consciousness that the observed lyotropic, and often thermotropic liquid crystallinity, of many biological materials that possess key biological functionality might be more than curious coincidence. Rather, as the survival of living systems depends on the flexibility and reformability of structures, it seems more likely that it is the combination of softness and structure of the liquid-crystalline state that determines the functionality of biological materials. The richest sources of liquid crystals derived from living systems are found in cell membranes, of these glycolipids are a particularly important class of components. In this critical review, we will examine the relationship between chemical structure and the self-assembling and self-organising properties of glycolipids that ultimately lead to mesophase formation.     

Chromonic mesophases

Over the last 10 years, there has been a growing acceptance of the concept of chromonic phases and a wider recognition that they form a well-defined family of lyotropic liquid crystalline phases, with a package of properties distinct in almost every aspect, from those of conventional amphiphiles. New chromonogenic compounds have appeared and new technological uses for chromonic systems are being actively explored. Recent promising investigations include the synthesis of a chromonic dye, C.I. Direct Blue 67, which has an N phase of high order parameter and which can be dried down to give well-oriented films of solid. When dried down on a ‘command surface’ of photoaligned substrate this can produce a highly patterned film. The use of chromonic phases in the construction of compensating plates for improving the viewing characteristics of twisted nematic displays has been explored. Although this technology may not be suitable for commercially exploitation in its present form, the success of the devices is significant. It is suggested that current studies of the way in which the temperature range of thermotropic discotic mesophases is enhanced in 1:1 CPI mixtures may well lead to improved formulations for chromonic dyes. It is predicted that the marriage of chromonic phase technology with current biochemical analytical techniques will give rise to a new generation of medical diagnostic tests.     

Catalysis of O-(para-nitrophenyl) O,O-dimethyl thiophosphate decomposition by chromonic mesophases based on polymerized ionic amphiphiles

The formation of a nematic chromonic mesophase in aqueous solutions of quaternized poly(ethylene imine) has been found using polythermal polarization microscopy. The reaction kinetics of O-(para-nitrophenyl) O,O-dimethyl thiophosphate hydrolysis has been studied by spectrophotometry, and a comparative analysis of the effects of lyotropic liquid crystals constructed as hexagonal and chromonic mesophases on this kinetics has been performed. It has been found that the hydrolysis of the substrate in a nematic chromonic mesophase is accelerated due to the concentration of the reactants.     

Narrowing of spontaneous emission and lasing in lyotropic and thermotropic liquid crystals

The narrowing of spontaneous emission and lasing are reported for the first time for a dye-doped lyotropic liquid crystal consisting of a methylbenzylamine solution of polybenzylglutamate (PBLG). Lasing was also studied in twisted nematics based on cholesterol derivatives. PBLG produces a cholesteric liquid crystal (CLC) with selective reflection in the visible region at PBLG concentrations above 55%. A comparison is made of the narrowing of spontaneous emission and lasing in lyotropic vs. thermotropic liquid crystals. In both cases lasing occurs where the selective reflection band overlaps the dye emission band. Thermotropic liquid crystals show a much lower lasing threshold than lyotropic systems. The lasing mechanism and the role of disorder in both systems are discussed.     

Chromonic/Silica nanohybrids: synthesis and macroscopic alignment

Some dye molecules self-aggregate to exhibit a lyotropic columnar liquid crystal state (chromonic liquid crystal) via pi stacking in relatively highly concentrated aqueous solutions. In this work, the chromonic liquid crystal structure was immobilized, for the first time, with silica networks by way of the sol-gel condensation process. The immobilization of the columnar structure was successfully attained in the presence of 2-(2-aminoethoxy)ethanol, which favorably mediates the interface between the anionic charge of the dye aggregates and the silica network. Without this molecule, the sol-gel process gave rise to a transformation from columnar to lamellar structure. Both spin-coating and dip-coating methods gave essentially the same results. In the dip-coated films, the dye molecules were aligned over a large area with orientation orthogonal to the lifting direction.     

Electrical conductivity of lyotropic and thermotropic ionic liquid crystals consisting of metal alkanoates

The electrical properties of ionic smectic liquid crystal (ISLCs), specifically, (i) oriented and non-oriented samples of lyotropic ISLC potassium caproate and (ii) oriented samples of thermotropic ISLC cobalt decanoate, are investigated in detail. The electrical conductivity of lyotropic smectic potassium caproate is higher than that of isotropic electrolytes. A giant anisotropy in the electrical conductivity of oriented samples of thermotropic ISLC cobalt decanoate is observed. The mobility of charge carriers in lyotropic ISLC is measured for the first time. The unusual electrical properties of ISLCs, which are governed by their layered structure, show that they have application potential in optoelectronic devices.     

The intercalation of ethidium bromide in the chromonic lyotropic phases of drugs and nucleic acids

Chromonic liquid crystalline phases are formed by a variety of drug and dye/water systems. In contrast to conventional lyotropic phases (where micelle formation underlies the mesogenic properties), in chromonic systems the molecules stack in columns. The different chromonic phases are different arrangements of these columns. We have examined the solution of ethidium bromide (EB) in the well-documented chromonic Intal/water system. EB is a widely used nucleic acid stain which changes colour when intercalated into DNA and which becomes fluorescent.

We have charted the changes in the temperature/composition phase diagram of the Intal/water system caused by adding EB. Although there are changes in the position of the phase boundaries, the overall pattern remains qualitatively the same—implying that the host phase is accepting EB as a similar chromonic molecule. The intercalation of EB molecules in the chromonic host phase results in optical effects—a metachromic colour change and fluorescence, similar to those occurring when the dye stains DNA.

These observations strengthen our belief that the central stack of bases in DNA can be regarded as being chromonic in nature.     

Influence of saddle-splay deformation on lyotropic chromonic liquid crystals confined between two coaxial cylinders

ABSTRACT

A striking feature of lyotropic chromonic liquid crystals confined in cylinder model exhibit double-twist director configurations. Evidence suggests that saddle-splay deformation is among the most important factors for the distortions of director. Previous researches limit the director to distort at a fixed plane (r-? plane) by using specific boundary conditions such as degenerate planar anchoring condition. In this work, we consider lyotropic chromonic liquid crystals confined between two coaxial cylinders with free-surface boundary conditions and Rapini-Papoular-type anchoring conditions. By using finite-difference iterative method to solve the numerical solution of Euler equation, we find that saddle-splay deformation leads to double-twist director configurations under free-surface boundary conditions, which consist of the result under degenerate planar anchoring conditions. Furthermore, at Rapini-Papoular-type anchoring conditions, saddle-splay deformation has a great influence on the director in the radial direction (r direction) and the director distorts in three-dimensional space. Remarkably, our method provides a more accurate theory basis for the measured values of saddle-splay elastic constant K_24。     

Polydispersity in liquid crystal systems

Here we discuss the statistical mechanics of polydisperse liquid crystal systems. Three different kinds of liquid crystal systems are treated: nematic order in thermotropic Maier-Saupe-like systems and in lyotropic Onsager-like rod systems, and smectic order in a perfectly aligned hard rod fluid. In the first two cases we calculate the broadening of the isotropic-nematic transition. In the last case the suppression of smectic order is dealt with. We discuss the relationship between real systems and the models discussed in the paper.     

Liquid crystals and life

The molecules of living systems invariably exhibit both thermotropic and/or lyotropic liquid crystalline properties. In some cases the mesophases formed by bio-materials have lamellar structures, whereas in other situations they form columnar phases. Many liquid crystal biomaterials are found in cell membranes, indicating that such structures have properties that are dependent on liquid crystallinity for their behaviour of a variety of bio-materials is discussed. function. In this article the mesomorphic