Nematic-smectic a tricritical phase transition in binary mixture of liquid crystals

Abstract

The nematic-smectic A tricritical phase transition has been studied in binary mixtures of liquid crystals. By making the analogy between the “quasi-binary” fluid mixture and binary mixture of liquid crystals, we adapt the thermodynamic model for fluid mixtures due to Griffiths to the case of mixtures of liquid crystals. In this study we obtained the temperature dependences of the smectic order parameter, nematic susceptibility and the specific beat discontinuity near the tricritical phase transition region of the binary mixture of liquid crystals. We then predicted the tricritical exponents for these quantities, which give the predictions of the non symmetric systems. Our prediction compare well with some experimental data for the binary mixtures of liquid crystals. This shows that the binary mixture of liquid crystals exhibiting NA phase transition can be described satisfactorily by the mean field model.