A type II aqueous cholesteric lyomesophase

Abstract

The lyotropic liquid crystals formed by optically active detergents, water, and electrolyte have been investigated near and above the water-rich limit of the lamellar mesophase by using nuclear magnetic resonance, relative density observations, and polarized microscopy. The racemic mixture of α-alanine decyl ester forms a lamellar phase, a disc-micelle type II phase (which may co-exist in equilibrium), followed by an isotropic material as the water content increases. The resolved d or l detergent also forms a lamellar mesophase which may coexist with a type II disc-micelle system; however, as water content increases a transition occurs to a cholesteric lyotropic mesophase which itself passes over to an isotropic phase at the highest water contents studied. The range of existence, as a function of water content, for these intermediate type II DM and cholesteric phases is very narrow. The screw axis of the cholesteric mesophase aligns parallel to the magnetic field. A tentative structure of the cholesteric phase based on disc micelles distorted into a partial helix is suggested.