Comparative Investigations of Light Transmission in Aligned and Non-aligned Textures of Homogeneous Mixtures of 4-n-alkyl-4'-Cyanibiphenyl Mesogens at Direct and Reverse smectic A <-> isotropic liquid Phase Transitions

Abstract

The thermo-optical properties of various types of textures (the homeotropic, planar, and tilted aligned and non-aligned textures) in liquid crystalline materials with smectic A mesophase have been investigated. Investigations have been carried out for large temperature interval and at the direct smectic A mesophase-isotropic liquid (SmA-I) and isotropic liquid-smectic A mesophase (I-SmA) phase transitions that have been carried out. Homogeneous mixtures of 4-n-octyl-4'-cyanobiphenyl with 4-n-decyl-4'-cyanobiphenyl were the objects of the investigations. Temperature dependences of the optical transmission for aligned and non-aligned textures have been measured. Temperature widths of the heterophase regions for the SmA-I and I-SmA phase transitions have been determined. The temperature shift in the optical transmission dependences to low temperatures for the reverse I-SmA phase transition temperatures and the thermal hysteresis has been found for the aligned and non-aligned textures.