Polymerization In Nonaqueous Lyotropic Liquid Crystals With A Polymerizable Solvent

Lamellar liquid crystals of lecithin and 2-hydroxyethyl methacrylate (HEMA) were polymerized by using UV radiation. Optical microscopy, infrared spectroscopy, and small-angle X-ray diffraction were used to compare the structure prior to and after polymerization. The lamellar structure was retained after polymerization with increased interlayer spacing. © 1987, American Chemical Society. All rights reserved

Single Compound Forming A Lyotropic Liquid Crystal At Room Temperature

The compound triethanolammonium oleate forms a lamellar liquid crystal at room temperature. The basis for the lyotropic mesomorphism is the fact that part of the triethanolammonium oleate has changed to triethanolamine and oleic acid. These two compounds serve as solvents in the liquid crystalline structure. © 1984 American Chemical Society

Surfactants And The Stratum Corneum Lipids

A simplified mixture of model stratum corneum lipids was mixed with different surfactants to make a preliminary estimation of the influence of surfactants on the stratum corneum lipid structure. The results revealed differences between cationic and anionic surfactants and between anionic surfactants with different structures. © 1998

Molecular Motion And Phases In An Equimolar Phosphatidylcholine/ethylene Glycol System

An equimolar mixture of phosphatidylcholine and ethylene glycol was studied by pulsed proton NMR at temperatures between 100 and 430 K. Relaxation times T1, T1ρ, and T1D, and second moments, M2, were measured. The system is lamellar liquid crystalline at room temperature, but at least four phases are present within the temperature range studied. Phase transitions were confirmed by DSC. Activation barriers were estimated for methyl reorientation, choline group motion, and chain motion. Models to describe the various motions and the role of spin diffusion are discussed. The relationship of the parameters for the present system to those for the corresponding aqueous phosphatidylcholine phase is briefly considered. © 1984 American Chemical Society

Formation Kinetics of an Emulsion in the System Water, Didodecyldimethylammonium Bromide, and Sodium Xylenesulfonate

The ternary phase diagram, the colloidal structures involved and the kinetics of an unusual emulsion formation in the system water, sodium xylenesulfonate (a hydrotrope) and didodecyldimethylammonium bromide (a surfactant) were determined using visual observation, optical microscopy, light scattering, electrical conductance and the stop-flow method. The results showed as expected that addition of the hydrotrope to the surfactant-water lamellar liquid crystal caused a disordering of it to an isotropic liquid, a microemulsion, but, surprisingly, for lesser hydrotrope/surfactant ratios the result of the addition was more ordered structures; a cubic liquid crystal and a plastic crystal. The results of stop-flow/light scattering analysis of the microemulsion-water mixing into an emulsion showed a marked reduction in scattering after mixing with decay times in the 2–3 seconds range but also the presence of anisotropic material which is found only outside the realm of mixing. This complex behavior after formation was explained by the difference in the kinetics of formation of different association structures

Water Permeation of Reaggregated Stratum Corneum with Model Lipids

Corneocytes were prepared from stratum corneum after extraction of the lipids and then were reaggregated with model lipids to form a membrane. The transport of water through the membrane was found to be similar to earlier published values for reaggregated stratum corneum formed with the indigenous lipids. Similar values were also obtained when only partially saponified free fatty acids were present as lipids. These results support an earlier hypothesis, that the lipid barrier to water penetration of the stratum corneum is determined by the structural organization of the lipids, not by the exact chemical structure of individual species

Food emulsion/ Edt . : Stig E . Friberg

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An investigation of the penetration of lipids in the bilayer of stratum corneum

Water is an essential component of the animal body and the prevention of its escape into the surrounding atmosphere is one of the important functions of the skin. The main barrier to water transport through skin is located in the outermost layer, the stratum Corneum (1,2). In this study, small angle X-ray diffractometry is used to determine the interlayer spacing in the layered structure and optical microscopy with polarized light is applied to give information about liquid crystal/crystal variations. Samples for the X-ray analysis were prepared by adding the lipids accordingly and water content for each series was varied from 30% to 40% water. The samples were mixed by centrifuging repeatedly through a constriction in a sealed 7 mm glass tube. The samples were then allowed to equilibrate at 30°C for 24 hours. Samples for photomicrography were prepared by transferring a small amount of sample onto a glass slide and sheared between the slide and cover to a thickness of about 5 to 10 microns and was observed between cross polarizers and photographed at a magnification of 200 times. Results showed that the unsaturated fatty acid/soap combination gave a lamellar liquid crystal. The optical appearance is typical of lamellar liquid crystal. Addition of the saturated fatty acids showed a typical optical pattern of a distorted lamellar liquid crystal due to the presence of crystalline lipidic material. The addition of cholesterol obviously returned the structure to the liquid crystalline state. Results of small angle X-ray diffractograms are given in Figure 1. The interlayer spacing of the unsaturated fatty acid/soap increased from 45.8A to 49.0A. Addition of the saturated acids caused no significant change in the interlayer spacing nor in the dependence on the water content. The behaviour after addition of cholesterol was entirely different and a strong dependence on the water content was found with an increase of 4A at the lowest water content but an increase of 10A at the highest water content

Surfactant Association Structures and the Stability of Emulsions and Foams

Traditional surfactants in combination with water and a more hydrophobic amphiphile, such as an alcohol or a carboxylic acid, present a rich variety of colloidal association structures, both micelles and lyotropic liquid crystals. The presence of such association structures has a pronounced influence on the stability of macrodispersed systems such as emulsions and foams. A few examples of such an influence are discussed.Peer reviewe