Study the Thermodynamic Properties of Liquid Crystal Systems Mixed With Small Molecules

Lattice model is appied to study the transition properties of liquid crystal under the influence of small spherical molecules as solutes. It is found that the transition temperature decreases if the interaction between molecules of solute and mesomorphic solvent is weak and increases for strong interaction with the increasing of solute concentration.
This model is also apllied to study the activity coefficient of non-mesogenic molecules as solute solved in liquid crystal. The theoretical results are compared with the data determined by gas chromatography experiments. In these experiments, the liquid crystal PBH_xB was used to separate three isomers m-,o-,p- nitrotoluence, and the activity coefficients. of the three isomers were determined at various temperatures. It is found that, in the considered region, larger potential between solute and solvent molecules corresponding to the larger activity coefficient and decreasing faster with increasing temperature.