ABSTRACT
This chapter discusses a small portion of the theoretical work on liquid crystals. The Landau-de Gennes theory is a phenomenological model for the nematic-isotropic phase transition. It is based on Landau’s general description of phase transitions and was first developed by de Gennes. The strengths of the Landau-de Gennes theory are its simplicity and its ability to capture the most important elements of the nematic-isotropic transition. A molecular theory is one that starts with the behaviour of single molecules and attempts to determine the characteristics of the macroscopic phase. Since large numbers of molecules are involved, such simulations routinely involve computer calculations. The Landau-de Gennes theory for the nematic isotropic transition can be extended to the smectic A-nematic transition. The use of new analytical techniques and the ability to use more powerful computers continue to refine our understanding of liquid crystals and the reasons behind their complex behaviour.
