Monte Carlo simulations of liquids of mesogenic oligomers

Monte Carlo simulations have been recently performed for model liquids of dimers and trimers consisting of rigid groups connected by semiflexible spacers. Though highly idealized, the models take into account the three principal factors responsible for the onset of nematic order in oligomers and polymers of this kind, i.e. the anisometry of the rigid groups, the anisotropy of their attractive interactions and the intrinsic conformational properties of the molecules under study. In a first set of simulations, the conformation of model trimers has been approximately regulated to mimic idealized systems of rigid groups separated by (CH2)(n) spacers with n odd or even. The simulated systems show reversible isotropic/nematic phase transitions at well defined temperatures, with odd-even oscillations in good agreement with experiments. The transitions are coupled with a conformational selection favoring extended conformations in the nematic liquids. Simulations of model oligomers with conformational properties approximating those of a well characterized series of mesogenic oligoesters are currently underway.