Optical properties of two liquid crystal compounds: a comparative study

The optical properties of two liquid crystalline mesogens S4 (code name) and S5 (code name) have been studied as a function of temperature. Our interest is to compare the macroscopic properties of these two thermotropic mesogens and to study the effect of replacing the OC6H13 group in S4 by NCS group to produce S5.With this aim in view the thermal variations of birefringence have been determined for both the compounds. The variations of polarizabilities with temperature have also been evaluated from density variations and birefringence studies and the thermal dependence of the order parameters of the two compounds have thereby been determined and compared. The theoretical values of the order parameters have also been calculated using the McMillan and Maier-Saupe potentials and compared with the obtained experimental values.