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

Investigations of mesomorphic and thermo-optical properties of lyotropic ne matic-calamitic (N-c) and nematic-discotic (N-d) mesophases are described. The peculiarities of microscopic textures and the temperature and concentra tion changes of the refractive index and birefringence have been studied. T he nematic-isotropic liquid phase transition temperatures and the temperatu re 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 accu racy. Thermic hysteresis in the width of heterophase regions of the phase transit ions between nematic mesophases and isotropic liquid have been found. (C) 2 000 Elsevier Science S.A. All rights reserved.