Refractive indices, order parameter and principal polarizability of cholesteric liquid crystals and their homogeneous mixtures Original Research Article

Measurements of refractive indices (ne,no) and birefringence (Δn) have been made in solid, cholesteric and isotropic phases of cholesteryl carbonate, cholesteryl stearate and their three homogeneous mixtures of concentration 0.25, 0.50 and 0.77 at varying temperature in the range of 18–35 °C. The results clearly indicates that various transitions are of the first order. For accurate measurement of Δn, a modified wedge method was used. Using ne and no, principal polarizability (αe,αo), internal field factor (γe,γo) and order parameter (S) have been evaluated, and their temperature dependence discussed. The order parameter has been determined by using the isotropic internal field model (Vuks approach) and the anisotropic internal field model (Neugebauerʹs approach), and both values agree up to average deviation of 0.7%.