Efeitos de campo elétrico em sistemas líquido-cristalinos envolvendo a fase esmética-C

Abstract

In the present work, we investigate the phase transitions in liquid-crystalline systems involving the smectic-C phase under the effect of an external electric field. Initially, a review of the theoretical model of Maier-Saupe, which describes the nematic-isotropic phase transition was performed, where we determine the behavior of the order parameter, which abruptly goes to zero at the transition temperature. We then approach the McMillan model, which is an extension of the Maier-Saupe model, including the smecticAnematic transition in our study. With this model we determine the behavior of the order parameters as a function of temperature and reproduce the phases diagrams. In addition, to these two well-known models, we have included in the work a brief review of the model developed by Govind and Madhusudana, which describes the smectic-C-smectic-A phase transition. This model motivated us to further study the smectic-C phase, which made us propose a new theoretical model on the liquid crystalline phase in question. With our model, it was possible to determine the properties of the system, which allowed us a more complete analysis and description of the phase transitions involving the smectic-C phase, in addition to using a smaller amount of descriptive model parameters. Finally, we analyze the effect of an external electric field on phase transitions involving the Sm-C phase, studying the changes in the thermodynamic and statistical properties of the system under such effect.