Showing papers on "Lyotropic liquid crystal published in 1989"

Surfactants in solution

Abstract: Surfactant fundamentals: branched versus linear hydrocarbon chains in surfactants ellipsometric evidence of anomalous refractive indices is contact angle hysteresis due to a film present behind a drop? STM molecular imaging of disordered molecular wires studies of morphology and phase behaviour of monolayers thermodynamics of adsorption of a cationic surfactant at solid-water interfaces. Micelles and microemulsions: pressure-jump studies on micellar relaxation time and its effect on various technological processes micellar catalyzed reactions in mixed solvent systems silica gels from microemulsions the state of water and surfactant in surfactant-based lyotropic liquid crystals polymerization of menthyl methacrylate and styrene in ternary emulsions and microemulsions. Polymer-surfactant interactions: polymer-surfactant interactions: effect of ionic strength, polymer charge and binding density on surfactant/polymer aggregates polymer-surfactant complexation in dilute aqueous solutions. Adsorption of surfactants: adsorption on high and low molecular weight natural surfactants at the crude oil-water interface and their influence on y-pH and y-time behaviour studies on asphaltenes and related petroleum fractions at interface influence of surfactants on the adhesion of clay particles to metal surfaces guidelines for the formulation, composition, and stirring to attained desired emulsion properties (type, droplet, size, viscosity, and stability) double emulsions stabilized by macromelecular surfactants. Biological applications of surfactants: interactions between the dispersed globules of W/O/W emulsions in the presence of proteins and saccharides the design and evaluation of a novel submicron amphotericin B emulsion in systemic murine cryptococcosis plant protein purification using cloud point extraction (CPE). Environmental aspects: environmental risk assessment of ethoxylated nonionic surfactants toxic spill remediation of chlorinated hydrocarbons via microemulsion formation.

Rheological properties of lamellar lyotropic liquid crystals

Abstract: Les proprietes rheologiques et la viscosite de cisaillement des cristaux liquides formes par du poly (oxyethylene) ether d'alkyle et de l'eau sont mesurees

A new soap/detergent/water lyotropic liquid crystal with a biaxial nematic phase

Abstract: A new lyotropic liquid crystal, potassium laurate, decylammonium chloride and water, which has two uniaxial phases and a biaxial nematic phase, is reported. A surface of the phase diagram and X-ray diffraction studies are presented. The chemical stability of this mixture is compared with the potassium laurate/decanol/water mixture. Optical measurements of the birefringence and X-ray studies indicate that this new mixture is more stable than the usual mixtures with alcohol.

Enzymes in lyotropic liquid crystal: a new method of bioconversion in non-aqueous media

Abstract: A new method has been developed for the use of enzymes as catalysts in organic solvents. The enzyme and cofactor are entrapped in a lyotropic liquid crystal which is insoluble in an organic solvent. The biocatalyst is significantly stabilized in this biphasic reaction system and product recovery is facilitated.

Structured aqueous detergent compositions containing salting-out electrolytes and surfactants and methods of forming them

Abstract: A structured aqueous detergent composition containing detergent-active material in the form of at least one detergent-active component and at least one electrolyte and having the following phases: (a) an isotropic aqueous solution forming a continuous phase; (b) distributed and suspended in said solution (a) discrete units of one or more non-network-forming phases, each selected from the following: (i) solid particles containing detergent-active material, (ii) lyotropic liquid crystals containing detergent-active material; and (iii) non-encapsulated liquid droplets containing detergent-active material, (c) one or more suspending phases which cause the composition to be structured so as to suspend the non-network-forming phase (b); said non-network-forming phase (b) having a higher concentration by weight of detergent-active material than said aqueous solution (a).

Lyotropic liquid crystalline solutions of hydroxypropyl cellulose in water: effect of salts on the turbidity and viscometric behavior

Abstract: Effect of addition of salt on the viscometric behavior of the dilute or concentrated aqueous solution of hydroxypropyl cellulose (HPC) was determined by means of an Ubbelohde or a cone-plate viscometer. That effect on the turbidity of the dilute system was also determined. As salts, NaCl, LiCl, and thiourea were chosen. The turbidity and viscometric behavior for the dilute system, and the viscometric behavior for the concentrated system were greatly affected by salt type and concentration. With increasing NaCl or LiCl concentration, the cloud point decreased, [η] showed a maximum, Huggins' constant k′ showed a minimum, and the shear viscosity for concentrated isotropic solutions showed a maximum. The 45 wt % solution with no salt showed a viscometric behavior which was characteristic of lyotropic liquid crystals; however, with increasing NaCl concentration, a critical temperature at which the shear viscosity showed a maximum with respect to temperature shifted to lower temperature. This behavior was due to an increase in the turbidity, not due to a phase transformation. On the other hand, an addition of thiourea did not affect so greatly the turbidity and viscometric behavior as an addition of NaCl or LiCl did. We speculated different actions of NaCl and thiourea.

Dynamic interactions between enzyme activity and the microstructured environment.

Abstract: A new approach for the study of an enzyme's relationship with its own reaction medium has been developed. One technique of micellar enzymology is the use of pseudohomogeneous systems composed of surfactant/water/organic solvent. In such systems, the physicochemical properties and textures of the medium depend on the relative ratios of the different components. Enzymes are catalytically active in such systems and up to the present have been studied in different microenvironments, such as micelles, microemulsions and lyotropic liquid crystals. Our purpose was to develop a system in which the enzyme could, by its activity, modify one of the components in such a way that the relative ratios among them changed sufficiently to produce a transition from one phase domain to another. The three components, water (or glucose in water), octanol and octyl-β-D-glucoside, form a classical ternary water/oil/surfactant system. The relevant phase diagram shows different macroheterogeneous phases and microstructured domains. The enzyme β-D-glucoside hydrolyses octyl-β-D-glucoside to form glucose and octanol. The enzyme was found to change the relative ratios of water (or glucose in water), octanol and octyl-β-D-glucoside in such a manner that the physicochemical structure of the medium was modified. At the beginning of the reaction β-D-glucosidase was present in a micellar solution of octyl-β-D-glucoside in water. As the enzymatic reaction proceeded, the medium became biphasic. One of the two phases was the micellar solution of octylβ-D-glucoside in water, while the other phase was either a microemulsion or a liquid crystalline phase. In addition the enzyme, through its catalytic activity, was able to modify the physicochemical properties of the reaction medium.

Fluorescence depolarization in macroscopically ordered uniaxial molecular samples. II. The ground- and excited-state interactions of fluorophores with ordered environment. A discussion of the published experimental data

Abstract: The model of fluorescence depolarization in ordered molecular systems, which assumes different ground- and excited-state interactions between the fluorescent molecules and the ordered environment, is discussed. A comparison of the results of the published studies aimed at experimental examination of this model is presented. It is concluded, that the fluorescence depolarization experiments on ordered lipid systems (lyotropic liquid crystals) require, in comparison with previous treatments, a more extended model. It is suggested, that such a model should account for the heterogeneity in ordering, motional and photophysical properties of fluorescent molecules when embedded in such systems.

Photochemically induced phase transitions in the system cetyltrimethyl-ammonium bromide-water containing N-methyl-N,N-diphenylamine

Abstract: Phase transition temperatures from lyotropic liquid crystals to the isotropic micellar solution of the system cetyltrimethylammonium bromide-water (CTAB-H2O) were measured in the presence of 0.1-0.9 weight % of N-methyl-N,N-diphenylamine (MPA). They were determined by optical and viscometric methods and were found to increase as a function of MPA concentration in solutions containing 21 and 23 weight % of CTAB. This effect was reversed when MPA was in situ photochemically converted to N-methylcarbazole, allowing photochemically induced phase transitions.

Lyotropic Liquid Crystals, Structures and Phase Transitions

Abstract: The most representative lyotropic liquid crystals are those formed by amphiphilic molecules, such as soaps, detergents and lipids, in presence of water. These molecules are able to build structures exhibiting a long range crystalline order, although they are disordered in a liquid-like manner at the local level. Their polymorphism is characterized by similar sequences of structures, whatever the details of the chemical structures of the molecules. These two characteristics, which will be discussed in the first part of the lecture, clearly show that the individual molecules can not be the building blocks of the structures and that the elements of structures are indeed the interfaces built by the molecules or, better, the symmetric films built by two facing interfaces. These structures can therefore be described as crystals of fluid films. In order to bring out a general basis for the understanding of this new class of crystals, we developed a model for studying periodic configurations of symmetric films, which will be presented in the second part of the lecture. Its basic hypothesis is the existence of a geometrical frustration resulting from the conflict between forces normal to the interfaces and forces parallel to the interfaces. We shall determine its possible solutions, as well as their sequence when its magnitude varies, following a geometrical approach similar to those developed for other cases of frustration in condensed matter physics.

Simple Theory for Persistent-Flexible Liquid Crystal Polymers Beyond the Second Virial Approximation

Abstract: Khokhlov and Semenov (KS) have proposed a theory for long persistent chains that quite accurately describes the liquid crystalline behavior of dilute solutions of long homogeneous bend-elastic macromolecules. By replacing their second virial description of excluded volume effects with Lee’s generalization of the Carnahan-Starling equation, results are obtained which are valid over a wider range of polymer concentrations. Comparison of the calculated order parameter and equation of state with experimental data for Poly(γ-benzyl-L-glutamate) yields good agreement for large polymer axial ratios, where rigid particle theories deviate strongly from experimental results. In addition, we show how this approach to persistent flexibility can be connected to a recent model for translational order in lyotropic liquid crystals.

Stabilization of lamellar oil–water liquid crystals by surfactant/ co-surfactant monolayers

Abstract: LIQUID crystals are divided into two main classes, thermotropic and lyotropic. Thermotropic liquid crystals are formed by melting, whereas lyotropic liquid crystals arise from the association of molecules, such as soap and water, that in general are not in themselves liquid crystalline. Thermotropic liquid crystals are used for liquid-crystal displays; lyotropic liquid crystals occur in living cells. Here we report a novel sequence of lyotropic liquid crystals comprising alternate layers of oil and water whose thickness varies linearly with the relative proportions of oil and water, and we have determined their structure using neutron diffraction methods. The oil and water layers are separated and stabilized by a monolayer film of surfactant and co-surfactant. The individual layers are typically a hundred angstroms or more in thickness, and total lamellar spacings of up to 1,000 A were observed. This behaviour is difficult to describe in terms of the theories of colloid stability currently used to describe lyotropic liquid crystals. An understanding of the self-organization of such systems over such large distances would elucidate how long-range liquid-crystalline ordering arises in living cells. Moreover, thermotropic liquid crystals are expensive and chemically relatively unstable, and lamellar mesophases of the lyotopic type described here could lead to inexpensive, chemically stable liquid-crystalline materials suitable for industrial application.

Synthesis and properties of poly(L-glutamic acid)s containing covalently bound 4-hydroxyphenylporphyrin moieties

Abstract: Poly(L-glutamic acid)s with various contents of 4-[10,15,20-tris(4-hydroxyphenyl)-5-porphyrinyl]phenoxy groups (polymers 3a–e) prepared by reaction of poly(L-glutamic acid) (1) and 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (2) in the presence of dicyclohexylcarbodiimide The structures of 3a–e in ethanol were studied by CD spectroscopy and it was found that the introduction of large amounts of porphyrin moieties into 3 tends to prevent the α-helix formation The IR dichroic ratios of films of 3a–e, obtained by rubbing the concentrated ethanol solution on an NaCl plate with a spatula into a constant direction, gave informations about the orientation of the α-helix rod X-ray diffraction photographs suggest that the crystalline packing of the α-helix is more disordered with increasing content of porphyrin moieties in 3 Polarizing microscopy indicates that 3a–d form lyotropic liquid crystals in concentrated DMF solution

Structures and Mechanisms of Phase Transitions in Surfactant Mixtures: Systems Which Induce the Ribbon Phase

Abstract: Phase transitions in lyotropic liquid crystal systems made from potassium palmitate/potassium laurate/water (KP/KL/H2O) and potassium palmitate/benzoyl alcohol/water (KP/BZA/H2O) were characterized by time resolved x-ray diffraction done at the SERC Daresbury (U.K.) Synchrotron Laboratory. Hysteretic phase behavior was observed for some of the KP/KL/H2O mixtures but not for any of the KP/BZA/H2O mixtures studied. In addition, the transition between the rectangular and ribbon phases in these systems is described using x-ray diffraction. General trends related to the observation of phase transitions in these systems are discussed. The ribbon phase appears to be more stable in the KP/BZA/H2O system since it retains its structure after the coexisting lamellar phase has transformed into a liquid crystalline bilayer for a larger temperature range than for KP/KL/H2O.

Aqueous detergent compositions and methods of forming them

Abstract: A structured aqueous detergent composition containing detergent-active material in the form of at least one detergent-active component and at least one electrolyte and having the following phases: (a) an isotropic aqueous solution forming a continuous phase; (b) distributed and suspended in said solution (a) discrete units of one or more non-network-­forming phases, each selected from the following: (i) solid particles containing detergent-active material, (ii) lyotropic liquid crystals containing detergent-active material; and (iii) non-encapsulated liquid droplets containing detergent-active material, (c) one or more suspending phases which cause the composition to be structured so as to suspend the non-network-forming phase (b); said non-network-forming phase (b) having a higher concentration by weight of detergent-­active material than said aqueous solution (a).

Process for the biocatalytic conversion of organic substances

Abstract: The invention relates to a biocatalytic process for the conversion of organic substances, especially those of low solubility in water. The invention is characterised in that enzymes, prokaryotic and eukaryotic cells or combinations of enzymes and cells are immobilised in lyotropic liquid crystals (mesophases), preferably with an inverse phase structure, and substrate supply and product removal are effected via one or more solvent phases. Organic solvents are used as solvent phases. It is also possible for an aqueous solvent phase to be present. These two- and three-phase systems are prepared by using three-component systems consisting of water, organic solvents and surfactant.

Influence of bridging additives on the phase boundaries and solvent properties of a nematic lyotropic liquid crystal

Abstract: Etude de l'influence de l'addition du salicylate de sodium sur la mesophase des solutions micellaires de bromure de tetradecyltrimethylammonium

Polymerization of lyotropic liquid crystals

Abstract: Polymerisation d'un ou plusieurs composants d'un cristal liquide lyotrope. Les proteines peuvent etre immobilisees a l'interieur de phases cubiques polymerisees

Liquid Crystalline Materials for Polymers with Anisotropic Ultrastructures

Abstract: : The in-situ polymerisation of reactive thermotropic and lyotropic liquid crystals affords a method of processing new polymers with anisotropic ultrastructures.

Liquid crystal display element and production thereof

Abstract: PURPOSE:To allow the application of a liquid crystal molecule oriented film with a uniform film thickness by forming the oriented film of a lyotropic liquid crystal polymer or thermotropic liquid crystal polymer having a mesogene group in the main chain or side chain. CONSTITUTION:The liquid crystal molecule oriented film is the water surface developed film of an org. high polymer and is constituted of the lyotropic liquid crystal polymer or thermotropic liquid crystal polymer having the mesogene group in the main chain or side chain. This high-polymer oriented film is crimped together with at lest a liquid crystal layer between a pair of electrode substrates at least one of which is light transparent. Problems such as generation of static electricity by a rubbing treatment, contamination of the boundary face of the oriented film and unequal display based on the nonuniformity in film thickness are eliminated in this way. Since the formation of the oriented film by the water surface development method is relatively easy and is highly mass productive, the easy mass production of the liquid crystal element is executed.

Method for the biocatalytic reaction of organic substances

Abstract: A biocatalytic method for reacting organic, especially poorly water-soluble substances. Enzymes, prokariotic and eukariotic cells or combinations of enzymes and cells are immobilized in lyotropic liquid crystals (mesophases), preferably with inverse phase structure. The supply of substrate and the removal of product are performed via one or more solvent phases. Organic solvents function as solvent phases. In addition, an aqueous solvent phase can also be present. In order to produce these two and three-phase systems, three-component systems consisting of water, organic solvent and surfactant are used.

Nematic Lyotropic Liquid Crystals as Media for Chemical Reactions

Abstract: An old theme in liquid crystal research, first introduced by Svedberg in 1916, is the examination of how chemical reactivity is modulated by the anisotropy of the medium to result in changes in rates of reaction or structures of product. We have recently returned to this problem by examining reactions in aqueous lyotropic nematic media. One can identify systems in which phase transitions occur from rod to disc to spherical aggregates of amphiphiles as functions of either temperature or concentration of surfactant, cosurfactant, or electrolyte, and study model reactions occurring through these phase transitions. One can orient the lyotropic medium in a magnetic field and assess the degree of ordering of reactant and product and their penetration into the micellar media by spectroscopic methods.