Lyotropic textures

Lyotropic liquid crystalline nanoparticles have also been described. Concentrated solutions of gold nanorods in water in the presence of a surfactant (cetyltrimethyl-ammonium bromide) display a nematic mesophase stable up to 200 °C [74[. The N mesophase was identified by optical microscopy by their typical nematic droplets texture. 

Figure 7.6 Fingerprint texture of lyotropic cholesteric double-headed arrow corresponds to pitch.

The smectic mesophases of the thermotropic liquid crystals show a variety of textures but resemble mainly the fan-shape texture of the lyotropic hexagonal meso-phase. For further reading more comprehensive literature is recommended [11]. 

Recently, Sato and Hatano 67 69) found a new type of chiral lyotropic mesophase composed of Tween 80, sorbitan mono-9-octadecenoate poly(oxy-l,2-ethanediyl), and water, and discussed the ICD of achiral solute molecules intercalated into the lyotropic mesophase. As the concentration of Tween 80 is increased, three distinct phases are obtained micelle, neat phase, and reversed micelle, in that order. In the region of the volume ratio of Tween 80/(Tween 80 + water) of 0.40 to 0.63 under crossed Nicol-prisms, a focal conic texture was observed. This result indicates that the... 

T extures of lyotropic mesophases have been the object of numerous observations by optical (1,2,3) and electronic (4, 5, 6,7) microscopy. Except for the pioneering work of Lehmann (1) and Friedel (2) who intended to identify the various kinds of defects which constitute the textures, the purpose of these observations was to recognize the different existing phases—lamellar, hexagonal (or in the soaps language neat phase, median phase, etc.)—in correlation with x-ray data. 

This study has concentrated on the defects observed in lyotropic lamellar phases, and it has put into evidence the specific character of the textures compared to classical thermotropic smectic phases. In leci-... 

Lyotropic liquid crystalline properties were observed for poly (arylamide) monodendrons derived from 1,3,5-substituted amino acid chloride hydrochlorides according to Kim [168]. These systems aggregate readily to form high molecular weight species in the absence of complexing ions. Amide solvents containing more than 40 wt.% of the dendrons exhibit nematic phase liquid crystalline texture under a polarizing microscope, whereas, 60 wt.% solutions produce a hard gel under static conditions. 

The junction zones of CAQ organogel networks are lyotropic microdomains that vary from hexagonal in decane to more compact, lamellar-like ordering in 1-octanol 94. Schlieren optical textures confirm the inhomogeneity of the orientation of the threadlike structures (Fig. 16), and CD spectra resemble those of neat CAQ solid, cooled from its mesophase. However, the solid morph obtained from solvent crystallization is packed differently from the gel strands 114. ... 

Evans et al. also showed that the 1 1 mixture of BAN and (3, y-distearoyl-phos-photidylcholine (DSPC) gives a smectic A texture in the temperature range of 57.3 to 100°C [21]. This is the first notice of lyotropic lamellar liquid crystals formed in the ionic medium. Additionally, Seddon et al. [28] and Neve et al. [29] have described the long-chained A-alkylpyridinium or l-methyl-3-alkylimidazolium ions to display smectic liquid-crystalline phases above their melting points, when Cl or tetrachloro-metal anions like CoCl " and CuCl " are used as the counter ions. Lin et al. have also noted the liquid crystal behavior of 1-alkylimidazolium salts and the effect on the stereoselectivity of Diels-Alder reactions [30]. However, liquid crystals are classified as ionic liquid crystals (ILCs), and they are distinguished from liquid crystals that are dispersed in ionic liquids. Although the formation of micelles and liquid crystal phases in ionic liquids have been thus reported, there has been no mention of the self-assembly of developed nano-assemblies that are stably dispersed in ionic liquids. In the next section the formation of bilayer membranes and vesicles in ionic liquids is discussed. 

Liquid crystalline polyguanidines 25 are obtained from the carbodiimide 24 also display a lyotropic nematic texture caused by strong dipolar-dipolar interaction between the main chain and side chains. ... 

The radius a of the onions in the intermediate shear-rate regime of lyotropic smectics depends on shear rate, scaling roughly as a A similar texture size scaling rule is found in nematics (see Section 10.2.7) there it reflects a balance of shear stress r y against Frank elastic stress. In smectics, the two important elastic constants B and Ki have differing... 

Walker, L. Wagner, N. Rheology of region I flow in a lyotropic liquid-crystal polymer the effects of defect texture. J. Rheol. 1994, 38 (5), 1525-1547. 

Fig. 36. Texture of the lyotropic mesophase of zwitterionic polysoap p-XX between crossed polarizers [357]...

Structures. The three types of mesomorphic phases are usually identified by using the polarizing microscope (11). The different types of lyotropic smectic mesophases can also be distinguished through their microscopic textures (26) by careful and detailed study. Using the microscope for such identifications is sometimes made more difficult by the tendency of the mesophases to orient when placed in contact with a surface. This orientation, of course, changes the microscopic textures. A mesophase in the presence of a crystalline phase may also be difficult to identify by microscopy. NMR can provide distinguishing characteristics which are unique for several mesophases. The use of the NMR characteristics for phase... 

Figure 24 Schlieren textures of the frozen lyotropic phase of (a) polymer 144b (R = 2-ethylhexyl = SiMes) (b) polymer 144b (R = (S)-3,7-dimethyloctyl R = SiMes) under cross-polarizers. The baton texture of polymer 144a (R = (S)-3,7-dimethyloctyl R" = SiMes) shown in (c) is indicative of a higher, lamellar order structure. (Adapted with permission of Wiley-VCH from Steffen, W. etal., Chem. Eur. J., 2001, 7, 117.)...

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