MICELLAR STRUCTURES IN LYOTROPIC LIQUID-CRYSTALS AND PHASE-TRANSITIONS

The formation of micellar nematics is discussed with emphasis on the transitions between nematic phases and nematic-smectic transitions. Phase diagrams for MTAB/1-decanol/D2O systems show a direct transition between uniaxial nematics. Electrical conductivity and birefringence measurements on a mixture of sodium decylsulfate, 1-decanol, and D2O demonstrate, on the other hand, the existence of a biaxial nematic range that separates the uniaxial nematics. On a mixture of cesium perfluoroctanoate and H2O the electrical conductivity and rotational viscosity are used to discuss the relevant features of nematic-lamellar-smectic transitions. The formation of elongated ribbon-like micelles at the nematic-smectic transition is suggested. Transitions between different nematic phases in the MTAB system may be connected with a structural change from long micelles with a fairly circular cross section to similar micelles with a more elliptical cross section.