Refractive and birefringent properties of 4-alkyl-4′-oxycyanobiphenyls at direct and reverse phase transitions

ABSTRACTStudies of temperature behavior of the mean refractive index, ordinary and extraordinary refractive indices, and birefringence have been carried out for three nematogens. The thermo-morphologic properties of the biphasic regions of the direct nematic-isotropic liquid and reverse isotropic liquid-nematic phase transitions have been investigated. The 4-n-alkyl-4′-oxycyanobiphenyls (n = 5, 6, 7) were objects of our study. Studies have been carried out for the circular cycle as the heating-cooling. Temperature behavior of the order parameter in nematic mesophase and at the nematic-isotropic liquid and isotropic liquid-nematic phase transition is discussed.