Microscopic Description of Nematic-Smectic A2 and Nematic-Smectic A1-Smectic A2 Phase Transitions in Binary Mixture of Polar and Nonpolar Liquid Crystals

Abstract

Abstract In the present paper, in a mean field approximation, we considered binary mixtures of polar and nonpolar liquid crystals (LC) with ideal orientational order. It is assumed that nonpolar molecules can form only monolayer smectic A-structure whereas polar molecules can form both monolayer smectic A-structure with short-range antiferroelectric order and bilayer smectic A-structure with long-range antiferroelectric order. By analogy with McMillan's theory the self-consistent equations determining order parameters for these smectic A structures are introduced. It is shown that smectic A1 phase with monolayer smectic A structure and smectic A2 phase with coexisting monolayer and bilayer smectic-A structures can ocur in the mixture. Phase diagram for mixture and entropy discontinuities at the nematic-smectic A1 and smectic A1-smectic A2 phase transitions obtained by numerical solution of self-consistent equations are similar to experimental ones. Also the temperature and concentration dependences of int...