THERMOTROPIC, REFRACTING AND THERMO-OPTICAL PROPERTIES IN THREE HOMOLOGS OF 4-N-ALKYL-4 '-CYANOBIPHENYLS

Abstract

Investigations of temperature behaviour of the mean refractive index n, ordinary n(o) and extraordinary n(e) refractive indices, and birefringence Delta n have been carried out for three homologues of 4-n-alkyl-4'-cyanobiphenyls (n = 8, 10, 12). The principal polarizabilities alpha(0) and alpha(e), effective geometry parameter alpha(eg) and average polarizability alpha(ave) have been calculated using the isotropic internal field model (Vuks approach). Temperature behaviour of the order parameter in regions of the smectic A-nematic, nematic isotropic liquid and smectic A isotropic liquid is discussed. All of the optical and orientational parameters, which have been obtained in this work, are in good agreement with the theoretical approach.