A computer simulation of model discotic dimers

We set up a model for discotic liquid crystal dimers and study, by means of Monte Carlo simulations, their phase behaviour and self--assembling properties, in comparison with the simpler monomeric case. Each discotic dimer is described by two oblate Gay--Berne ellipsoids connected by a flexible spacer, modelled by a spring of three different lengths. We find that dimerization in general yields produces a significant change on the phase behaviour, with an increase of the columnar--nematic transition temperature, a widening of the nematic region and the apparent suppression of the crystalline phase in favour of the columnar phase up to very low temperatures. Longer spacers prove to ease the formation of columns and to increase the orientational order.