Optical Microscopy, X-Ray Diffraction, and Dielectric Permittivity Studies in Binary Mixtures of Nematogens Showing Induced Smectic Phase

The binary mixtures of nematogenic compounds 4-n-pentyl phenyl 4-n′-hexyloxy benzoate (ME6O.5) and 4-cyanophenyl 4-heptyl benzoate (CPHB) show the presence of induced smectic phase. In the present paper we report the phase diagram of the binary system (ME6O.5+CPHB) obtained by polarizing optical microscopy as well as the results of X-ray diffraction and static dielectric permittivity measurements on the system throughout the entire composition range. The observed variation of dielectric anisotropy with molar concentration in the induced smectic phase region is explained by assuming molecular associations in the mixture which is supported by our measurements of layer spacing in the induced smectic phase by X-ray diffraction studies.