Showing papers on "Lyotropic liquid crystal published in 1975"

Temperature, concentration, and molecular weight dependence of the twist elastic constant of cholesteric poly‐γ‐benzyl‐L‐glutamate

Abstract: Aspects of the behavior of the twist elastic modulus K22 of a lyotropic liquid crystal formed by the α‐helical polypeptide poly‐γ‐benzyl‐L‐glutamate of three molecular weights (MW= 300 000, 310 000, and 550 000) in three solvents (dioxane, dichloromethane, and chloroform) were investigated as a function of concentration and temperature. We find that K22 in this system may be made to vary over a wide range by adjustment of solvent and polymer molecular weight. Only a slight concentration dependence of K22 throughout the liquid crystal range was, however, noted. The variations can be at least partially understood in terms of changing macromolecular interactions and recent statistical hard‐rod theoretical treatments of liquid crystal elasticity. The functional form for the temperature dependence of the order parameter was also determined for the system through the clearing point.

Circular Dichroism in Lyotropic Liquid Crystals of Polyglutamate Solutions

Abstract: A poly-γ-ethyl-L-glutamate solution with a cholesteric color exhibits a circular dichroism due to the selective reflection of circularly polarized light of one sense by the cholesteric helical structure existing in the solution. On the other hand, an induced circular dichroism is observed in the wavelength region corresponding to the absorption bands of an achiral dye molecule when the molecule is dissolved in the poly-γ-benzyl-D-glutamate liquid crystalline phase. The two modes of circular dichroism are correlated to the structure and the chirality of the cholesteric phase of concentrated polyglutamate solutions.

Studies of Lyotropic Liquid Crystals

Abstract: NMR studies of liquid crystalline substances have been extensively used to derive information on the mesophase structure, molecular arrangements, mobilities and mechanism of binding of small ions or molecules. Such studies of lyotropics are particularly important since these systems have fairly well-defined physical and chemical properties and can serve as models for the more complicated biological systems [166, 167]. The smectic liquid crystalline lipid-water phase serves as a particularly good model for the study of some properties of biological membranes since both biomembranes and lecithin-water mixtures have a bilayer structure [168–175]. The mechanism of binding of ions and molecules in lyotropic liquid crystals provides a deeper insight into these aspects of passive membrane functions.

Nuclear magnetic resonance of sodium methylphosphonate in a lyotropic liquid crystal

Abstract: A method has been developed and applied to sodium methylphosphonate for determining the values of J HX from the temperature dependence of the anisotropic motion of the solute. The method reduces the uncertainty of D HX due to solvent effects on J HX. As in methyl fluoride discrepancies are observed between structural parameters calculated from different sets of observed dipolar couplings. Unlike the case of methyl fluoride, correction of the dipolar couplings for vibrations improves consistency of these values. Large correction terms found in the present molecule result from contributions of low frequency vibrations whose excited states are appreciably populated at room temperature. The structural parameters and anisotropic motion determined in a lyotropic mesophase are discussed.

Lyotropic Liquid Crystals and Biological Membranes: The Crucial Role of Water

Abstract: No collection of papers on liquid crystals would be complete without some discussion of lyotropic liquid crystals and biological membranes. At the present time these two subjects constitute areas of intensive research effort providing a literature of rapidly increasing size. The high current interest mandates a discussion of these topics, but at the same time makes it very difficult to select the material to be presented in the limited space available. The discussion in this chapter will therefore be confined to two main topics, (1) the composition and structure of lyotropic liquid crystals and biological membranes and (2) the nature of the principal interactions that give rise to their existence and stability.

Studies of Molecular and Ionic Species Dissolved in the Nematic Phase of Lyotropic Liquid Crystals

Abstract: Nuclear magnetic resonance spectra from molecules oriented in the nematic phase of liquid crystals are interpretable in terms of chemical shift tensor, σ, indirect, J, and direct, D, coupling tensors, as well as, for nuclei of spin greater than 1/2, quadrupole tensors Q.

Lyotropic Liquid Cystals in Stagnation Flow: Fibrinogen

Abstract: A lyotropic liquid crystal, a concentrated fibrinogen solution, was formed in a two-dimensional axial stagnation flow field. The stagnation surface was a water permeable but fibrinogen impermeable ...