Showing papers on "Lyotropic liquid crystal published in 1995"

Shear-Induced Alignment of a Hexagonal Lyotropic Liquid Crystal as Studied by Rheo-NMR

Abstract: The shear-alignment process of the hexagonal lyotropic liquid-crystalline phase formed by a solution of hexa(ethylene glycol) monododecyl ether (C 12 E 6 ) in heavy water is examined. Experiments were performed with a novel cone-and-plate rheo-NMR apparatus, which allows the simultaneous measurement of shear viscosity and deuterium nuclear magnetic resonance. The NMR spectra show that initially disordered samples having polydomain structures become macroscopically aligned during shear. The aligned state shows no relaxation after cessation of shear. With proceeding shear alignment, the apparent shear viscosity decreases. The changes of the deuterium NMR spectra observed during the alignment process reveal that the reorientation of the domains depends not on the shear rate but on the shear strain. NMR experiments using different shear geometries show that at shear rates of ca. 2 s -1 the hexadic axis becomes aligned parallel to the flow. At lower shear rates, we cannot yet distinguish between an orientation of the micelles in the flow direction or perpendicular to the shear plane ; an orientation along the flow direction, however, appears more likely.

On the Area Neutral Surface of Inverse Bicontinuous Cubic Phases of Lyotropic Liquid Crystals

Abstract: The location of the area neutral surface in lyotropic liquid crystalline membranes plays a critical role in the phase behavior of all the mesophases which possess curved interfaces. In this paper a mathematical formalism is developed which allows the experimental determination of the area neutral surface from X-ray structural measurements of the inverse bicontinuous cubic phases. The theory is used to determine the location of the area neutral surface in monoolein (Chung, H.; Caffrey, M. Biophys. J. 1994, 66, 377-381) and didodecyl-β-D-glucopyranosyl-rac-glycerol (Turner, D. C.; Wang, Z.-G.; Gruner, S. M.; Mannock, D. A.; McElhaney, R. N. J. Phys. II Fr. 1992, 2, 2039-2063). The results indicate that the area neutral surface is located between the C 1 and C 3 positions on the hydrocarbon chains. However, the X-ray and gravimetric data currently available on these systems appears to be of too low a precision to allow one to check for the presence of any net stretching. An error analysis of the theory is used to provide an outline prescription for a new generation of experiments which will allow us to determine the presence of stretching in bicontinuous cubic phases

Amphitropic liquid-crystalline properties of some novel alkyl furanosides

Abstract: Monoalkyl substitution in carbohydrate systems is known to affect the melting behaviour of sugars and support the introduction of thermotropic liquid-crystalline phases. Similarly, the inclusion of a relatively long aliphatic chain in the molecular structure affects the formation of lyotropic liquid crystal phases. In some instances, long-chain-substituted carbohydrates can generate both lyotropic and thermotropic phases, and hence these materials have been described as amphitropic. Here, the thermotropic and lyotropic liquid-crystalline properties of an amphitropic family of monoalkylated furanosides are described. In addition, the thermal behaviour of the materials is discussed in terms of simple molecular models of geometrically optimised structures, and the resulting degree of hydrogen bonding possible for the various materials.

Liquid crystal display device and its production

Abstract: PURPOSE:To adhere two sheets of substrates without receiving high heat and UV rays in a liquid crystal material, such as thermotropic liquid crystal or lyotropic liquid crystal, by sticking these substrates to each other by a soluble fluororesin, then injecting the liquid crystal into the gap between the substrates. CONSTITUTION:Two sheets of holding plates 21 made of stainless steels are arranged above and below the substrates 11 and are clamped in the state of clamping two sheets of these holding plates 21 by means of supporting bolts 17 and nuts 18 via compressing springs 19. The soluble fluororesin of an intermediate member 12 for sealing cures in this state at room temp. The inside of a chamber where two sheets of the substrates 12 holding the intermediate member 12 for sealing is arranged is evacuated to a vacuum to evacuate the gap 14, by which the liquid crystal material, such as thermotropic liquid crystal or lyotropic liquid crystal, is injected into the gap 14 from an injection port 13. The member for sealing of the soluble fluororesin is fixed to this intermediate after the end of the packing of the liquid crystal to close the injection port 13, by which the liquid crystal is hermetically sealed.

Shear orientation of a lamellar lyotropic liquid crystal

Abstract: Shear orientation of a lyotropic lamellar liquid crystalline phase of tetra ethyleneglycol mono dodecylether, C12A4 in water was studied by combined rheo-small-angle light scattering. Shear thinning was observed with a sample of 500 μm thickness. The scattering patterns showed that domains were aligned and stretched in flow direction. Shear thinning was also observed with a thinner sample, but caused a strong change in light-scattering pattern. A maximum of scattering intensity was observed at finite scattering vector and shifted to a higher scattering vector with increasing shear stress. This observation can be explained by a fragmentation of domains at high shear stress and is supported by a mosaic texture observed in optical microscopy.

Simulation of self-assembly and lyotropic liquid crystal phases in model discotic solutions

Abstract: A prototype model of amphiphilic discotic binary solutions is proposed, and its statistical mechanics investigated by Monte Carlo computer simulation procedures. Data are presented from a large number of simulations, over 50 separate systems in all, carried out at a single relatively low pressure but covering almost the entire temperature-composition range of phase space beyond the melting line, including successful simulations of equilibrated cluster distributions throughout the isotropic solution phase. These data are in agreement with the well known theory of linear aggregation, but a major surprise is found in that the associated equilibrium constant possesses a strong concentration dependence at low temperature. The global aggregation behaviour is described in detail and discussed in the context of the standard state that is usually invoked when applying linear aggregation theory to experimental systems. It is concluded that as the temperature decreases the ideal behaviour of these cluster distributi...

Organic lyotropic lamellar liquid crystals

Abstract: 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.

Amphiphilic liquid-crystalline networks - phase behavior and alignment by mechanical fields

Abstract: A cross-linked polysiloxane carrying non-ionic amphiphilic side-groups attached with their hydrophobic end to the polymer backbone is synthesized. The amphiphilic groups are selectively deuterated at the α-position of the hydrophobic alkyl chains. The phase behavior with water is studied by deuterium nuclear magnetic resonance spectroscopy. A lamellar phase (La) is observed on the low-water-concentration side of the liquid-crystalline regime. The domains of the La-phase can be aligned macroscopically by uniaxial compression of the sample.

Mixtures of branched non-ionic oligo-oxyethylene surfactants in aqueous solutions- the effect of molecular geometry on LC phase behaviour 4

Abstract: The LC phase behavior of ternary mixtures of the two corresponding branched non-ionic surfactants 1,3-bis-(methoxy-tetraoxyethylene)-2-propoxy-tetradecane (Y-surfactant) and 1,3-bis-(heptyloxy)-2-propoxyoctaoxyethylene mono-methyl ether (V-surfactant) and water were studied by polarizing microscopy. The two branched surfactants, which have different molecular geometries but nearly the same hydrophilic-lipophilic volume ratio, exhibit extremely different phase behavior in binary surfactant/water systems. For the ternary mixtures of Y- and V-surfactant and water we found-according to established packing models-a continuous stabilization of the cubic and hexagonal phases and a destabilization of the lamellar phase with increasing amount of Y-surfactant. On the other hand, we observed a thermal stabilization of the lamellar phase. The maximal transition temperatures of the lamellar phase pass a maximum with increasing amount of Y-surfactant.

Effects of Ionic Strength on the Supramolecular Structure in Liquid Crystalline Solutions of Persistent Length DNA Fragments

Abstract: Cholesteric liquid crystals of persistence length DNA fragments (contour length 55 nm) were studied with small angle neutron scattering. The cholesteric axis was oriented either perpendicular or parallel to the incoming neutron beam with the help of a magnetic field in the range 0.8-1.65 T. A single diffraction peak is observed, which shows in the perpendicular configuration an angular anisotropy in intensity. A moderate magnetic field strength dependence of the anisotropy has been observed, but at the higher field strength the liquid crystal is nearly completely aligned. A decrease in peak intensity as well as anisotropy is observed with increasing ionic strength, but futed DNA concentration. This indicates a decrease in position and orientation order with increased screening of electrostatic interactions. From a comparison of the anisotropic data to the scattering contribution of a single fragment, the standard deviation of the presumed Gaussian orientation distribution could be derived. The results compare favorably with the second virial theory of lyotropic liquid crystals, provided that electrostatic interactions in terms of an ionic strength dependent effective diameter and DNA flexibility are taken into account.

Gelation of Fully Acylated Cellobiose in Alkane Solution

Abstract: Cellobiose octa(decanoate), a discotic columnar mesogen, was found to form in hexadecane solution various molecular assemblies such as a lyotropic liquid crystal of discotic columnar type, multimolecular micelles, and a thermoreversible gel, depending on the concentration and temperature. The gelation, observed even at very low concentrations, say, < 0.01 weight fraction of the mesogenic compound, is believed to proceed by local coagulation of long threadlike micelles into micro-liquid-crystallites, which work as cross-linking points combining the threadlike micelles. This will be a new type of gel that could be termed a “liquid crystalline gel.”

Electrochemical measurements of anisotropic diffusion in thin lyotropic liquid crystal films using interdigitated array electrodes

Abstract: A new application of interdigitated array (IDA) electrodes is described for diffusion measurements of electrochemical probes dissolved in thin, lyotropic liquid crystalline films. The liquid crystal is a solution of 32% (w/w) lithium 4-trans-n-pentyl cyclohexanoate (Li5CH) in water, which can be prepared as well-ordered films of thickness less than ca. 12 {mu}m. Apparent diffusion coefficients (D{sub APP}) of the electrochemical probes are calculated from steady-state currents of generator/collector voltammograms. The diffusional anisotropy, measured parallel and perpendicular to the liquid crystal director, increases with increasing hydrophobicity of the probes. A simplified model has been developed to explain the diffusional anisotropy of hydrophobic probes in the ordered film. The transition temperature of the liquid crystal is determined from an activation plot of D{sub APP} for 1,1{prime}-dimethylferrocene. 32 refs., 6 figs., 1 tab.

Synthesis of inorganic gels in a lyotropic liquid crystal medium. I. Synthesis of silica gels in lamellar phases obtained from non-ionic surfactants

Abstract: Some lamellar phases made with aqueous lyotropic liquid crystals were used as templates for the gelation of a silica inorganic network from tetramethylorthosilicate (TMOS). The aim was to synthesize materials with an anisotropic texture.

Multifractality of lyotropic liquid crystal formation of aluminium dodecylbenzenesulphonate

Abstract: The formation of colloidal and liquid crystalline aggregates of aluminium dodecylbenzenesulphonate caused by mixing aqueous solutions of A1(NO3)3 and dodecylbenzenesulphonic acid (HDBS) was investigated by light scattering and polarizing microscopy. Applying a fractal approach, some aggregates can be considered as multifractals and some as fractals, depending on the slopes of the ‘lgl(Q) versus lg Q’ plots (for multifractals the slopes are > 3). A model of multiscaling for the calculation of fractal dimensions in the formation of the liquid crystalline phases is proposed, describing both the spacial and the temporal dependence of amphiphile self-aggregation. The basic symmetries of the dynamics of formation and the structures of the liquid crystalline phases were found to be consistent.

Process for preparing a porous or pseudoporous anisotropic material, with a ceramic polymer lattice.

Abstract: The present invention concerns the preparation of a porous or "pseudoporous" anisotropic material. The anisotropic material consists of a conglomerate including, on the one hand, discreet micellar units with a configuration which is at least partly tubular and with a structure of the lyotropic liquid crystal type and/or the impressions thereof, and, on the other hand, a matrix based on ceramic polymer with alkoxide recurrent elements, in which the said units and/or their impressions are included, characterised in that it consists essentially of: mixing an ionic surfactant, water and at least one alkoxide in proportions chosen so that a lyotropic liquid crystal structure can form and a condensation hydrolysis reaction allowing the polymerisation of the alkoxide recurrent elements can take place and optionally eliminating the micellar units so as to make the material porous. The present material can be used for example as a carrier for active molecules in linear and non-linear optics and in catalysis.

Molecular interactions and formation of lyotropic liquid crystals of hydroxyethyl cellulose acetate

Abstract: The relationship between the hydrogen bond (H-bond) interactions and the formation of the cholesteric liquid crystalline phase was studied by Fourier transform infrared spectroscopy (FTIR), refractometry and polarizing microscopy. It was quite evident that the H-bonding played an important role in the early stage of the formation of cholesteric liquid crystalline phase in hydroxyethyl cellulose acetate (HECA)/dimethyl sulfoxide (DMSO) solutions and the rigidity of the HECA chains was more important to form liquid crystalline phase than molecular interactions when the concentration is very high.

Enantiomeric excess analysis of (2R, 3S)-3-deuterio-2-methylcyclohexanone and (1S, 2R, 3S)-3-deuterio-2-methylcyclohexanol, through deuterium NMR in a polypeptide lyotropic liquid crystal

Abstract: Poly-γ-benzyl-L-glutamate (PBLG) and dichloromethane form a lyotropic liquid crystal which can be used as solvent for enantiomeric excess analysis of molecules containing several stereogenic centers, through deuterium NMR spectroscopy. All isomers of 3-deuterio-2-methylcyclohexanone and of 3-deuterio-2-methylcyclohexanol dissolved in PBLG/CH 2 Cl 2 solvents, exhibit different quadrupolar splittings on their deuterium NMR spectra, which allows an accurate determination of their diastereoisomeric and enantiomeric excesses.

Textures and defects in lyotropic liquid crystals of ethyl-cyanoethyl cellulose

Abstract: Textures and defects in ethyl-cyanoethyl cellulose [(E-CE)C]/dichloroacetic acid (DCA) cholesteric liquid crystalline solutions and in (E-CE)C/polyacrylic acid (PAA) composites were observed and studied by polarizing microscopy and electron microscopy. The existence of χ, λ and τ disclinations were observed in the mesophase with disk-like and band-like textures. Pairs of disclinations with different signs were also found in the mesophase with the band-like texture. Domain walls were observed in (E-CE)C/PAA composite films with cholesteric order by TEM. The orientation of polymer chains in the vicinity of the core of the disclinations is discussed.

Reentrant Uniaxial-Biaxial Transition in Poly-Ethylene-Glycol Doped Lyotropic Liquid Crystals

Abstract: Interferometric measurements of the effect of a polymer gradativelly added in a lyotropic liquid crystal is reported here. Studies of the phase diagram, birefringence and critical exponents as a function of the polymer concentration are presented. Measurements of the optical birefringence as a function of temperature are performed with the micellar system potassium laurate, 1-decanol, and water doped with variable quantities of the polymer poly-ethylene-glycol (PEG). The transitions from the calamitic nematic phase to a reentrant discotic-biaxial-discotic phase were observed when increasing the PEG molar concentration. Our results confirm the critical properties of the uniaxial-to-biaxial nematic transition. The critical exponent for the order parameter (β = 0.38) obtained for the sample without PEG is in god agreement with the value caculated for the XY model. Some results with higher PEG doping concentration indicate that β is higher than 0.38 leading to the mean-field value.

Liquid-crystalline polysurfactant

Abstract: A new kind of amphiphilic polymer (PAMC16S) has been synthesized where the amphiphilic moiety is attached as a side chain via the hydrophilic end to the polymer backbone. DSC, POM, and WAXD study revealed that the polysurfactant formed thermotropic liquid crystalline phase. The liquid crystalline domains appeared after annealed at the melt for a period of time, and evolved with annealing. It was indicated that the thermodynamic effect played a significant role on the self—aggregation of hydrophobic ends, so as to form liquid crystalline structure. X—ray investigation suggested that the mesophase structure could be described as smectic with lamellar type of packing, in which alkyl tails aggregated to form layer. A model of supermolecular structure was given.

Effects of weak shear on hyperswollen lyotropic smectic liquid crystals

Abstract: We have developed a Zimm-type viscometer specially designed for the simultaneous measurements of the structure factor and the viscosity of hyperswollen lyotropic liquid crystals under a very weak shear. We have investigated the shear effects on the layer undulation fluctuation in the lamellar structure and the transition from the anisotropic lamellar to the isotropic sponge phase. We have found a significant difference in the rheological properties between the lamellar and the sponge phase: The former exhibits non-Newtonian flow behavior, while the latter exhibits Newtonian behavior.

Study of Lyotropic Liquid Crystals Containing Nonionic Surfactant of TX-10

Abstract: Lyotropic liquid crystals from nonionic surfactant (TX-10), styrene, and water were studied at 30℃ to determine the phase regions and obtain some typical photographs by using microscope with polarized-light And the geometrical dimensions were determined by low angle X-ray diffractrion The X-ray data showed that the structure of mesophase disclosed lamellar liquid crystals with Bragg spacing ratio of 1:1 / 2:1/3… For these lamellar liquid crystals the results indicated a linear increase of the interlayer spacing with addition of water or styrene and pronounced decrease with addition of TX-10 in the system The 2H NMR methods were specially applied to determine the exact liquid crystals' structure It was found that the structure varied from mixed W/O type microemulsions and lamellar liquid crystals to single lamellar liquid crystals to single hexagonal liquid crystals to hexagonal liquid crystals and O / W type microemulsions in the liquid crystal region with the addition of the water These results were discussed theoretically

Hydrogen-Deuterium Isotopic Effect in Lyotropic Liquid Crystals

Abstract: The study of structural reconstructions in liquid crystalline phases of mesomorphic lecithin-water system due to the hydrogen-deuterium isotopic replacement was made by the positron annihilation and infrared spectroscopy methods. The changes in values of parameters of molecular interactions stipulated by such isotopic effect were obtained from the analysis of experimental and theoretical data.