PHASE-EQUILIBRIA OF A NEMATIC AND SMECTIC-A MIXTURE

A phase diagram of a mixture consisting of nematic and smectic liquid crystals has been calculated self-consistently by combining Flory-Hugg ins (FH) theory for isotropic mixing and Maier-Saupe-McMillan (MSM) th eory for smectic-A ordering. However, the MSM theory can be deduced to the original Maier-Saupe (MS) theory for nematic ordering. To describ e the phase transitions involving induced smectic phase and nematic smectic equilibrium, two nematic and two smectic order parameters for the nematic/smectic mixtures have been coupled through the normalized partition function and the orientation distribution function. Self-con sistent numerical solution has been sought in establishing nematic/sme ctic phase diagrams involving (i) phase separation between nematic and smectic liquid crystals and (ii) occurrence of induced smectic in a n ematic/smectic mixture. The predictive capability of this combined FH/ MSM theory has been tested critically with a reported phase diagram of a nematic/smectic liquid-crystal mixture and also with our experiment al phase diagram of a mixture consisting of a nematic side-on side-cha in liquid-crystalline polymer and a smectic low molar mass liquid crys tal. (C) 1998 American Institute of Physics.