Optical and dielectric parameters of a laterally difluorinated phenylbicyclohexane liquid crystalline compound

Abstract

The temperature variation of the refractive indices in the nematic range of a laterally difluorinated phenylbicyclohexane liquid crystalline compound was determined using the thin prism technique. Birefringence and effective geometry parameter of this LC compound was calculated from the measured refractive indices. Using a four-parameter model, the temperature variation of the refractive indices and birefringence was theoretically fitted. The compound is found to have low value of birefringence and high value of effective geometry parameter. Using refractive index data, three different methods were used in this work to obtain temperature dependence of order parameter, namely Vuks’ method, Haller approximation method, and method based on effective geometry parameter. All of them show the same trend. The temperature variation of dielectric permittivities of the compound was done at frequency 1 kHz by an LCR meter. The temperature variation of dielectric anisotropy of the compound was calculated from the experimentally measured values of dielectric permittivities. The compound shows moderate negative dielectric anisotropy.