Optical studies of a binary liquid crystal mixture exhibiting induced smectic A phase

A binary liquid crystalline mixture of a monotropic polar compound 4-cyanophenyl 4'-n-pentyl benzoate (CPPB) and an enantiotropic non-polar compound 4-n-hexyl phenyl 4-n'-pentyloxy benzoate (ME5O.6) shows the presence of an induced smectic A phase in the region 0.1 <= x(CPPB) <= 0.82, where xCPPB is themole fraction of CPPB. The results of texture study, density study and refractive index measurements of the eutectic mixture along with those of the pure samples are reported in this paper. The density values of the eutectic mixture are found to be much higher than that of the pure samples. The determination of order parameters of the pure samples and eutectic mixture has been carried out. In order to determine the order parameters of the samples, we have used different methods, Vuks', Neugebauer's, modified Vuks' and direct extrapolation method. The results of order parameters obtained from the different approaches are compared and analysed in detail.