Optical properties of nematic liquid crystal (C21H27NO2S) under AC/DC electric fields

Abstract

In this study, the effects of the phase transition on the optical transmittance of the nematic liquid crystal C21H27NO2S, 4'-isothiocyanatophenyl-4-pentylbicyclo[2,2,2] octane-1-carboxylate are investigated in terms of temperature variation and rotational angle of the polarizer through electro-optical methods under AC/DC electric fields. It is observed that the domain structure of the material is affected considerably by the applied electric field as the temperature changes. Under applied electric fields, the crystal-nematic (CN) phase-transition point changes and the behaviour of the liquid crystal in the phase-transition region shows some differences. The intensity of the light passing through the system under a DC electric field increases as the electric field rises. Nevertheless, the intensity of the transmitted light under an AC electric field increases at the beginning and then decreases as the electric field rises to a temperature of more than 355 K. These results can be explained through the formation of a domain structure during the phase-transition process and the light scattering caused by these structures.