Behavior and properties of lyotropic-nematic and lyotropic-cholesteric phases

The formation of lyotropic mesophases in systems of tetradecyldimethylaminoxide/water/aliphatic alcohol was examined in dependence on alcohol concentration and alcohol chain length (heptanol, octanol, nonanol, decanol). The ternary phase diagrams were established. The following lyotropic phases were detected by microscopic texture observation: hexagonal phase (H), lamellar phase (L a), rodlike nematic phase (N C), and disklike nematic phase (N D). The positions of the corresponding regions in the phase diagrams were determined. In particular, the N C- and N D-phase were of special interest. — Lyotropic-cholesteric phases were induced in the lyotropic-nematic phase region by adding optically active components such as cholesterol, tartaric acid, lithocholic acid. When subjected to the influence of a magnetic field, these cholesteric phases show the socalled spaghetti-like texture. The textures have been used for determining the pitch length. A linear relation between pitch length and concentration of the optically active components was established.