Lyotropic lamellar phases

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-... 

Roux, D. (1993). Rheology of lyotropic lamellar phases. Europhys. Lett., 24, 53-58. 

Nallet, R, Laversanne, R. and Roux, D. (1993) Modelling X-ray or neutron scattering spectra of lyotropic lamellar phases Interplay between form and structure factor. /. Phys. II France, 3, 487-502. 

Some of the chloro-bridged palladium 105a (R = C H2 +1, R = OC H2m+i), a mixed-bridged /r-acetato /r-thiolato 106b ( = ot = 6), and a mononuclear complex 111 (R R, R, R = OCioH2i) discussed above were also found to exhibit additional lyotropic mesophases in contact with apolar organic solvents such as linear alkanes (octane, decane, dodecane, and pentadecane), cycloocta-1,5-diene, and the chiral limonene. A lyotropic lamellar phase was induced for the dichloro complexes with symmetrical chain length (n = m = 6, 10) in linear alkanes the transition temperatures were found to decrease from pentadecane to octane. 

Figure 9 Schematic drawing of the membrane structure of lyotropic lamellar phases. The lamellar phase can be swollen either with water (hydrophilic solvent) or oil (hydrophobic solvent), leading to direct or inverted bilayers. The membrane thickness is (5, d is the smectic repeat distance. (From Ref 111.)...

Fig. 3.22 A molecule of potassium (K) laurate with deuterium (D) label (a) and a structure of the lyotropic lamellar phase (b)...

Helfrich W (1994) Lyotropic lamellar phases. J Phys Condens Matter 6 A79-A92... 

Since a lyotropic lamellar phase with tilted and chiral molecules has the same polar C2 point group symmetry as the thermotropic SmC phase, the important question emerges, whether the lyotropic SmC phase might also show ferroelec-tricity and polar electro-optic switching like its thermotropic counterpart. 

Salmon JB, Manneville S, Cohn A (2003b) Shear banding in a lyotropic lamellar phase. I. Time-averaged velocity profiles. Phys Rev E 68(5) 051503... 

Wunenburger AS, Cohn A, Leng J, Arneodo A, Roux D (2001) Oscillating viscosity in a lyotropic lamellar phase under shear flow. Phys Rev Lett 86(7) 1374-1377... 

Zipfel J, Berghausen J, Lindner P, Richtering W (1999) Influence of shear on lyotropic lamellar phases with different membianes defects. J Phys Chem B 103 2841-2849... 

As mentioned above, the lyotropic lamellar phases of soap-alcohol-water mixtures [15] or of phospholipid-water dispersions may also be ordered homeotropically. Ordered layers up to 0.5 mm thickness may be produced. The orientation is effected simply by sucking the dispersions into flat glass cells with an inner diameter 0.5 X 10.0 mm. The torque generated by the hydrodynamic shear orients the membranes in such a way that their normals are directed perpendicular to the glass surface. 

Parallel contours are also evident in smectic phases viewed under a polarizing microscope. In the case of smectic C phases, for example, these contours are due to the helical periodicity, while in smectic E and lyotropic lamellar phases they occur when defects accumulate along certain lamellae or groups of lamellae. 

The main patterns present in these textures are shown in Fig. 5 for lyotropic lamellar phases and in Fig. 32 for thermotropic liquid crystals. 

In these lectures we have seen that the lyotropic lamellar phase exhibits in a pronounced manner, the Landau-PeierIs effect for dilute stacked membrane systems with low rigidity k(> = kgT. The x-ray structure factor was seen to exhibit power-law behavior with the exponent (d) describing the algebraic decay of layer correlations. In turn, f (d) is directly related to the intermembrane interactions. 

Conversely, Ti (i.e., in practice linewidth) measurements allied to (estimated) values of the quadrupolar coupling constants have been used to determine r<. and hence to study the motional behavior of various species. Thus t<. increases with the hydrocarbon chain-length in aliphatic ethers, and in acetone 0 measurements can give information not available from C, H, or H owing to rapid methyl group rotation. Cyclic ketones, cyclic ethers, and crown ethers and their complexes have also been studied, as have water reorientation in a lyotropic lamellar phase and motions of the sulfate ion in aqueous solution. Detailed studies of polynuclear osmium carbonyl dynamics have been undertaken, and allied to... 

Lyotropic lamellar phases are made by equidistant organic bilayers regularly separated by water or oil. Some of these lamellar phases show very interesting textures of FCD s. This is the case when the lamellar phase is between two phases of different topology. In the system studied by Boltenhagen et a/.(1991,1992), both types of FCDI and II have been observed. 

Oily-streaks are the most usual structural defects in lyotropic lamellar phases. They appear as long bands with a complex inner structure, which subdivide the sample into so-called homeotropic regions where the layers are parallel to the boundaries of the preparation, and thus appears in black between cross nicols. 

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