Analysis of the Tilt Angle for a Binary Mixture of C7-70PDOB Liquid Crystal Close to the Smectic A–Smectic C* Transition

Abstract

The tilt angle θ is calculated as a function of temperature close to the smectic A- smectic C* (AC*) transition for the liquid crystal C7 and its binary mixtures of 70PDOB with the concentrations (mol %) of X = 0, 5.15, 9.68, 15.0 and 19.4. The experimental data from the literature are analyzed for these binary mixtures using the mean field models with the free energies expanded in terms of the order parameters (tilt angle θ and the spontaneous polarization P). In the mean field models, the biquadratic P²θ² and P²θ² + Pθ (bilinear) couplings are considered, and the coefficients in the expansion are calculated for the concentrations X (70PDOB) in this binary mixture of C7+70PDOB. Our mean field predictions are satisfactory and they explain the observed behaviour in this liquid crystalline system.

Keywords:

• Liquid crystal
• mean field model
• phase transition