Enhanced smectic a mesophase in mixtures of two terminally polar compounds

Abstract

An enhanced smectic A phase has been observed in mixtures of two terminally polar compounds, viz, 5-(4-n butylphenyl)-2-(4-cyanophenyl)-pyrimidine (4 PCPP) and n-dodecyl-4-(4'-nitrobenzoyloxy) benzoate (12 NBOB). The former is a nematogen and the latter non-mesomorphic with a hidden smectic A-isotropic transition. The smectic A-nematic transition boundary shows a parabolic shape, but with an unusually large tilt angle between the axis of the parabola and the composition axis. Mixtures in some composition range exhibit the reentrant nematic phase. Xray diffraction studies indicate that the smectic phase is of the A_d type. Low frequency dielectric constants and dispersion measurements of ε_Verbar; are also reported.