Influence of phase transitions on the electro-optic properties of nematic liquid crystals

The objectives of this thesis are, first, to study correlation between thestructure and phase transition of some nematic liquid crystals by using optical andelectrooptical methods, and second to analyze phase transition between nematic andisotropic phases.First of all we studied in detail optical anisotropic properties of three nematicliquid crystals: 4?-(Octyloxy)-4-biphenylcarbonitrile, 4?-(Pentyloxy)-4-biphenylcarbonitrile, 4?-isothiocyanatophenyl-4-pentylbicyclo[2.2.2]octane-1-carboxylate by using polarizing microscope. We determined the domain structures innematic phase of 4?-(Octyloxy)-4-biphenylcarbonitrile, 4?-(Pentyloxy)-4-biphenylcarbonitrile, 4?-isothiocyanatophenyl-4-pentylbicyclo[2.2.2]octane-1-carboxylate liquid crystals and influence of temperature (T) to domain structure.Then we determined the optical transmission for 4?-isothiocyanatophenyl-4-pentylbicyclo[2.2.2]octane-1-carboxylate liquid crystal with and without electricfield (AC & DC) and observed anomalies of the optical transmission in the region ofnematic-isotropic phase transition.KeyWords: Nematic liquid crystals, optical transmission, electrooptic effect, phasetransitionsII