THERMO-OPTICAL STUDY OF AZO-DYE DOPED NEMATIC LIQUID CRYSTALS AS FLEXOELECTRIC GUEST-HOST SYSTEMS

Photosensitive flexoelectric nematics were formed as guest-host systems by mixing of azo-dye mesogens with the nematic liquid crystal 4-butyl-cyclohexane carboxylic acid 4-pentyloxy-phenyl ester. The produced binary systems were characterized by their thermo-optical properties. The UV light-induced shift of the clearing temperature (the isotropic-to-nematic phase transition temperature) of the mixtures is due to molecular conformation (cis- and trans- isomers) of the azo-dye dopant upon UV light illumination at a wavelength in the absorption region. The corresponding change in the thermal behaviour of the dielectric properties of the mixtures was also evidenced.