Negative optical anisotropic behaviour of two higher homologues of 5O. m series of liquid crystals

In this paper, we report optical studies of two higher homologous of 5O. m (m = 14,16) series which are found to exhibit negative optical anisotropy in our studies. These compounds are calamatic interdigitated with unsymmetrical alkyl chain length. The compounds show high refractive indices in our experiment. The experimentally measured refractive indices data used to calculate the molecular polarizability, order parameter, Lorentz and internal field factors. We observed that, the molecular polarizability of both the sample increases with the increase in temperature. Vuks' and Neugebauer's models are adopted for the calculation of molecular polarizabilities. Direct extrapolation method for birefringence measurements and Vuks', Neugebaur's, modified Vuks' based on Haller's extrapolation methods were used to determine the order parameter of the LC compound. The results from our study show the same nature for both the liquid crystal compounds.