Hexagonal liquid-crystalline structure

Microemulsion gels are usually based on nonionic ethoxylated ether surfactants based on oleyl, lauryl, or isocetyl alcohol either alone or in combination with ethoxylated phosphate esters. Long hexagonal liquid crystalline structures present in the gel can vibrate when the container is tapped, resulting in a ringing gel [18], Table 10 presents a versatile ringing gel microemulsion base formula from ICI [16] for three clear cosmetic products. 

Kunieda, H., Umizu, G., and Aramaki, K. (2000) Effect of mixing oils on the hexagonal liquid crystalline structures. 

Fig. 2.20. Phase diagram (at 25 °C) from the work by Ekwall and co-workers (cf. Refs.8 86)) for the three-component system hexadecyltrimethylammonium bromide (CTAB) - hexanol -water. Li denotes a region with water-rich solutions L2 a region with hexanol-rich solutions D and E are lamellar and hexagonal liquid crystalline phases, respectively. In the figure are also schematically indicated the structures of normal (Lj region) and reversed (L2) micelles as well as of the liquid crystalline phases. (From Ref.9Sb...

Structure and Polymorphism of Lipopeptides. Amphiphilic lipopep-tldes Cjj(AA)p exhibit mesophases in aqueous solution for water concentrations smaller than about 60 %, The structure of the mesophases and of the dry lipopeptides obtained by evaporation of the mesophase water at a slow rate was determined by X-ray diffraction. Lipopeptides X-ray diagrams obtained are similar to those exhibited by classical amphiphiles (11). They have allowed us to establish the existence of three types of liquid-crystalline structures Isunel-lar, hexagonal and cubic. 

Highly ordered lamellar gel microstructures are formed by certain surfactants and mixtures of a surfactant and long-chain fatty alcohols in water. Using small angle X-ray scattering (SAXS), an ordered lamellar stack lattice model was proposed for the gel formed by 10% w/w cetostearyl alcohol containing 0.5% cetri-mide surfactant. In contrast, the microstructure of a Brij 96 gel depends on the surfactants concentration. A hexagonal liquid-crystalline gel structure was... 

Fig. 14 Hexagonal close-packed liquid crystalline structure of the object and its transformation in to an isotropic liquid state...

The special restriction caused by tying low molecular mass liquid crystalline substances to a polymer chain was also illustrated with amphiphilic liquid crystals. A hexagonally close-packed structure of rod-like micelle cylinders of sodium 10-undecenoate with about 50% water lost during polyma-ization at 60 °C its structure and became isotropic. On cooling, a lamellar liquid crystalline structure, more suitable to accommodate the macromolecular backbone was found. Bas l on the discussions of Sect. 5.3.4 it is likely that with longer side-chain amphiphiles condis crystals could be grown in analogy to the soaps described in Sect. 5.2.3... 

Some cosmetic products are in the form of microemulsion gels. This name has emanated from the cosmetics industry from a colloidal viewpoint these gels are liquid crystals with cubic or hexagonal symmetry. The liquid crystalline structures per se are not the subject of this chapter reviews in that area are readily available [1-4]. 

Amar-Yuli et al. combined the potential of both liquid crystalline structure as well as glycerol as cosolvent to enhance insulin thermal stability and moderate the aggregation progress [49]. Insulin was incorporated into several modified reverse hexagonal systems based on friendly surfactant and polyols to explore the impact of the protein confinement on its stability, unfolding behavior, and morphology with severe external conditions, low pH, and higher temperatures (up to 70 °C). 

For all copolymers studied (copolymers containing between 18 % and 83 % of polypeptide] the liquid crystalline structures are always lamellar and are very similar to the structure of saccharide-peptide block copolymers. In the lamellar structure of copolymers with a polyvinyl block and a hydrophobic polypeptide block, each sheet of thickness d results from the superposition of two layers one of thickness d/ formed by the polyvinyl chains in a more or less random coil conformation, the other of thickness dg formed by the polypeptide chains, in an a helix conformation, arranged in an hexagonal array, and generally folded ( 7, 8]. ... 

Twelve oxyethylated fatty alcohols with various lengths of alkyl chain and ethylene oxide were used in this investigation. In view of numerous literature data available, physicochemical tests were limited to measurements of surface tension, wettability and viscosity. Microscope photographs were taken in polarized light in order to confirm the appearance of liquid crystalline structures. As expected, formation of micelles was observed at low concentrations, whereas mesophases (hexagonal and lamellar) were identifled at concentrations of about 50% to 70%. 

The mono-olein-water phase diagram (Figure 15c) shows the formation of lamellar liquid crystalline structure at room temperature (20 °C) at water content between 2 and 20%. At higher water concentrations, a cubic phase is formed, which above 40% water exists in equilibrium with water. If the temperature of the cubic phase is increased above 90 °C, a hexagonal II phase is produced. 

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