Showing papers on "Lyotropic liquid crystal published in 1986"

Novel types of ionic thermotropic liquid crystals

Abstract: Liquid crystals are usually categorized as either lyotropic mesophases in which fluid anisotropy results from polar headgroup packing of amphiphilic molecules, or as thermotropic mesophases where the orientational order arises from interactions between partially rigid anisotropic molecules. The phase types exhibited by lyotropic and thermotropic liquid crystals have distinctive structures, optical textures and physical properties. Inclusion of a rigid anisotropic moiety into a lyotropic liquid crystal gives an additional source of orientational ordering, and can lead to phase behaviour encompassing both thermotropic and lyotropic liquid crystals. We have prepared a series of silver-containing thermotropic liquid crystals based on the bis(stilbazole) silver (I) cation. Some members of this series, in association with the amphiphilic counter-ion lauryl sulphate, form liquid crystal mesophases characteristic of both lyotropic and thermotropic liquid crystals.

Designing new lyotropic amphiphilic mesogens to optimize the stability of nematic phases

Abstract: The factors which govern the stability of lyotropic amphiphilic nematic phases are delineated and then used to design mesogens which give rise to stable NC and ND phases on dissolution in water The synthesis and phase behaviour of novel discoid amphiphiles, designed to form NC phases, are described

Study of Lyotropic Liquid Crystals in Viscometric Flow and Elastohydrodynamic Contact

Abstract: Lyotropic liquid crystals of triethanolammonium oleate in several nonaqueous solvents were prepared and characterized. Their rheology and elastohydrodynamic contact behavior were investigated. Under the conditions studied, they are non-Newtonian, shear thinning fluids whose behavior up to shear rates of 2500 s−1 can be described by a rheological equation. In elastohydrodynamic contact, at high pressure/high shear, they had effective viscosities larger than would be predicted from their low shear rate behavior, perhaps due to a limiting shear stress condition. They behaved as homogeneous liquid crystalline fluids and, like greases, certain formulations exhibited a tendency to starve the contact. Presented at the 42nd Annual Meeting in Anaheim, California, May 11–14, 1987

Electron-microscope observation of the smectic-nematic transition in a lyotropic liquid crystal.

Abstract: Observation de la transition a partir de la phase nematique miscellaire en disques vers la phase lamellaire smectique du melange chlorure d'ammonium-chlorure de decylammonium

Possible Defect-Mediated Phase Transition in a Lyotropic Liquid Crystal. Electron Microscopy Observations

Abstract: A lamellar lyotropic phase (aqueous solution of nonionic C12E6) is studied in the vicinity of a lamellar-to-isotropic phase transition. We use freeze fracture and electron microscopy to show that, as temperature increases: the concentration of screw dislocations increases, screws of the same sign build twist walls and screws belong to dislocation loops which cross layers. Within reach of the transition, the burst of the number of defects induces a disorganization of the lamellar phase into small blocks, disoriented one with respect to another and bounded by twist walls. To our knowledge this is the first experimental evidence of a defect-mediated phase transition.

The swelling of a lamellar lyotropic liquid crystal by an alkane

Abstract: Etudes par diffraction RX du gonflement de la phase lamellaire du systeme de: P-octylbenzenesulfonate de Na-pentanol-eau en presence de decane

Lyotropic liquid crystalline phase behaviour of a monomeric and a polymeric monosaccharide amphiphile in aqueous solution

Abstract: Monomeric and polymeric amphiphiles were synthesized which exhibit lyotropic liquid crystalline phases in aqueous solution. The hydrophobic group of the monomeric surfactant is a dodecane-group esterified with acrylic acid. The hydrophilic unit is a monosaccharide derivative. By radical polymerization the monomer (N-D(-)-gluco-N-methyl-(12-acryloyloxy)-dodecane-l-amide) is converted into the corresponding polymeric surfactant. The monomer as well as the polymer exhibit a lyotropic 1.c. phase of lamellar structure. Owing to the polymerization the regime of the lamellar phase is greatly enlarged for the polymer, compared to the monomeric sufactant. These results confirm earlier investigations on non-ionic ethylene-glycol surfactants.

Branched lipopeptide polymers forming thermotropic and lyotropic liquid crystals, their applications and corresponding monomers

Abstract: Branched polymers resulting from homopolymerization or copolymerization of monomers of formula I: ##STR1## R is H or a lower alkyl group of C 1 to C 3 ; Z is O or NH; B has the formula: --(CH.sub.2).sub.q1 --Z.sub.1 --(CH.sub.2).sub.2 -- in which q1 and q 2 are integers greater than or equal to 1, the sum of which is less than approximately 32 and Z 1 represents a single bond or O, S, NH, CO or CO--NH; (AA) p represents a peptide radical comprising p linked aliphatic alpha-aminoacids, bound at B by its carboxyl group, each amino acid comprising less than 15 carbon atoms and being possibly substituted at one carbon atom of the chain by a carboxylic acid or ester, amide or amine group, the terminal amine group of the peptide radical being possibly acylated by a R'CO group, R' being an alkyl radical comprising 1 to 4 carbon atoms, or by any other group stable under the conditions of synthesis; and p represents a number ranging between 1 and 200. Application as thermotropic and lyotropic liquid crystals and emulsifying and foaming agents.

Formation of Lyotropic Liquid Crystals of Cellulose Derivatives Dissolved in Inorganic Acids

Abstract: Formation of Lyotropic Liquid Crystals of Cellulose Derivatives Dissolved in Inorganic Acids

Occurrence of liquid-crystalline mesophases in microemulsion dispersions

Abstract: Although microemulsion dispersions have compositions which are related to lyotropic liquid crystals, their possible structures are not normally considered to be crystalline. As described here, small-angle neutron diffraction spectra have been obtained from some oil–water microemulsion dispersions, and display peaks which correspond to lamellar, hexagonal and cubic arrangements, similar to those observed in lyotropic liquid crystals. The formation of these liquid crystal mesophases (mesomorphic phases) seems to be a general feature of microemulsion compositions and not an isolated example.

Optical birefringence and temperature range of the biaxial nematic phase in a lyotropic liquid crystal

Abstract: A linear relation is found between the cube of the optical birefringence and the temperature range of the biaxial nematic phase in the lyotropic mixtures of potassium laurate, l‐decanol, D2O. Such a relation which is consistent with the Landau model of the uniaxial to biaxial nematic phase transitions may be used as a criterion for preparing samples of the desired temperature range of the biaxial nematic phase.

Pretransitional behavior at the reentrant nematic-isotropic phase transition in a lyotropic liquid crystal.

Abstract: Magnetic susceptibility measurements are reported for the ternary system potassium laurate, 1-decanol, and ${\mathrm{D}}_{2}$O below the reentrant isotropic-nematic phase transition. The susceptibility was found to diverge with increasing temperature and exhibit a mean-field-like exponent. The results are analyzed and discussed in terms of micellar anisometry controlling the supercooling temperature and thus driving the reentrant transition.

Preparation of organic color filter

Abstract: PURPOSE:To form an org color filter easily and simply by exposing lyotropic liquid crystals forming a cholesteric phase in a photobridgeable solvent to UV rays using a light valve as a mask CONSTITUTION:The lyotropic liquid crystals 2 forming a cholesteric phase in the photobridgeable solvent are held between a pair of thin transparent bases 1, 1', and this panel holding them is exposed to UV rays 4 using the light valve 3 as the exposure mask to form a colored layer with a desired form between the pair of bases 1, 1'