Molecular theories and computer simulations of liquid crystals

Two different approaches are adopted for the study of the properties of liquid-crystalline systems: molecular theories and computer simulations. The development is described of a molecular field theory for calculating the thermodynamic properties of liquid crystals containing flexible chains. The application of this theory to a variety of flexible model mesogens is discussed and the results compared with experimental data. In an attempt to rectify the deficiencies in this model, an alternative parameterization is presented of the molecular field theory based on the molecular moment of inertia tensor. The predictions of this new parameterization are compared with those of the previous approach and thermodynamic data obtained from experiment. The conformational probabilities calculated with the original theory are used in a study into possible visual representations for flexible mesogens. Techniques involving fixed and conformational dependent reference frames are explored and the results analyzed with the aid of computer graphics. The possible relationships between the graphics images and order parameters determined from NMR spectroscopy are discussed. Next, a molecular dynamics simulation of particles is presented in the microcanonical ensemble interacting via a single-site anisotropic potential which has been parameterized to model both rod-like and disc-like mesogens. The phase behavior together with the static and dynamic properties of these systems are discussed and compared with results of other simulations of liquid crystals and experiments.