Lyotropic nematic mesophases: investigations of mesomorphic and thermo-optical properties

Investigations of mesomorphic and thermo-optical properties of lyotropic nematic-calamitic (N-c) and nematic-discotic (N-d) mesophases are described. The peculiarities of microscopic textures and the temperature and concentration changes of the refractive index and birefringence have been studied. The nematic-isotropic liquid phase transition temperatures and the temperature widths of heterophase regions of the phase transitions from the N-c and N-d mesophases to the isotropic phase have been determined with a high accuracy. Thermic hysteresis in the width of heterophase regions of the phase transitions between nematic mesophases and isotropic liquid have been found. (C) 2000 Elsevier Science S.A. All rights reserved.