Liquid-crystal hexagonal

Different types of liquid crystals exhibit different rheological properties [16,17]. With an increase in organization of the microstructure of the liquid crystal its consistency increases and the flow behavior becomes more viscous. The coefficient of dynamic viscosity r, although a criterion for the viscosity of ideal viscous flow behavior (Newtonian systems), is high for cubic and hexagonal liquid crystals but fairly low for lamellar ones. However, the flow characteristics are not Newtonian but plastic or pseudoplastic, respectively. 

Figure 5.11 Proposed arrangement of polysilane molecules in the hexagonal liquid-crystal mesophase.

Fig. 2.18. Phase diagram of the dodecyltrimethylammonium chloride-water system. F denotes isotropic solution phase, M normal hexagonal liquid crystal, N lamellar liquid crystal and C and C cubic liquid crystalline phases. (From Ref.84))...

These structures are commonly referred to as hexagonal liquid crystals. As the surfactant concentration is further increased, the tubules expand in a second direction to form large, stacked lamellar sheets of surfactants, commonly referred to as lamellar Hquid crystals. These Hquid crystals are very important in soap making. 

By y-ray irradiation at room temperature, ZnS nanowires were grown, in which the crystal growth was in situ templated by an inverted hexagonal liquid crystal formed from oligo(ethylene oxide)oleyl ether amphiphiles, n-hexane, n-hexanol/ isopropanol (2/1) and water [151]. Nanocrystalline jS-ZnS (sphalerite) was prepared in aqueous isopropanol solution [152]. The TEM images (Figure 7.36) indicate that the product from mercaptoethanol is most well dispersed, and that from thiourea... 

Fig. 7.11. Schematic representation of a silica membrane material exhibiting an ordered porous texture. Template effect obtained from self-assembled amphiphilic systems, (a) Wet gel ccmfeiining a hexagonal liquid crystal phase and the corresponding X ray diagram. G ) Heat-treated gel with residual ordered porosity and the corresponding X-ray diagram [68].

Figure 13. Phase transition temperature of the system of isotropic solution and hexagonal liquid crystal. Pure CTAB-HjO, CTAB-HjO + 0.62% 9-anthracene carboxylic acid before irradiation, x after irradiation at 366 nm, after reirradiation at 280 nm, O. From Ref. 155 with the permission of VCH Veriagsgesellschafl.

Figure 3. The optical pattern of the hexagonal liquid crystal. Figure 4, is distinctly different from that of the lamellar one. Figure 2.

Figure 4. The hexagonal liquid crystal contains close-packed cylinders.

Figure 4 Part of the phase diagram of the system Triton X-100-decanol-H2O. Li, O/W region L2, W/0 region D, lamellar liquid crystal region E, hexagonal liquid crystal region. (From Ref. 37.)...

Figure 1 A phase diagram of a system composed oflipids extracted from cereal lipids and water. The weight fraction of each component is given in the diagram. L3, sponge phase LC, liquid crystal LC-L, lamellar liquid crystal and LC-H, reverse hexagonal liquid crystal.

Figure 4 A phase diagram of a system composed of monoolein and water. One representative structure of a bicontinuous cubic liquid crystalline phase is shown to the right. L, lamellar liquid crystal Hn, reverse hexagonal liquid crystal and Li, reverse micellar phase.

In the second case, the plates match with each other and one gets stacks of them. The most effective packing is of the stack-to-stack type, leading to the hexagonal liquid crystal packing. 

Watanabe J, Takashina Y (1991) Columnar liquid crystals in polypeptides. 1. A colunmar hexagonal liquid crystal observed in poly(y-octadecyl L-glutamate). Macromolecules 24 3423-3426... 

Studies of domain size of hexagonal liquid crystals in C12E08/water/alcohol systems. Langmuir, 17, 7245-7250. 

I. Amar-Yuli, Hexagonal liquid crystals and hexosomes structural modifications and solubilization. Ph.D. dissertation, The Hebrew University of Jerusalem, Israel, 2008... 

D. Libster, P. Ben Ishai, A. Aserin, G. Shoham, N. Garti, Prom the microscopic to the mesoscopic properties of lyotropic reverse hexagonal liquid crystals. Eangmuir 24, 2118-2127 (2008)... 

D. Libster, A. Aserin, N. Garti, Interactions of biomacromolecules with reverse hexagonal liquid crystals drug delivery and crystallization applications. J. Colloid Interf. Sci. 356, 375-386 (2011)... 

Of course, the surfactant molecules can also phase separate to form micelles within the solvent as shown in Fig. 10.30, in addition to other liquid aystal phases which can strongly influence particle nucleation and growth. Fot example, the formation of a hexagonal liquid crystal phase for 55% Tween surfactant dissolved in 45% water caused crystal growth of copper sulfate to be much inhibited, producing monosize dispersions of crystals around 2 pm in diameter. ... 

The hexagonal liquid crystal is a high-viscosity fluid phase composed of a close-packed array of cylindrical assemblies of theoretically unlimited size in the axial direction. The structures may be normal (in water) in that the hydrophilic head groups are located on the outer surface of the cylinder, or inverted, with the hydrophilic group located internally. 

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