Influence of polydispersity on the phase behavior of colloidal liquid crystals: A Monte Carlo simulation study

Using isobaric semigrand Monte Carlo simulations, we have investigated the phase behavior of a model for polydisperse rodlike colloids. The system consists of hard spherocylinders in the limit of infinite aspect ratio, with polydispersity in the length of the particles. If the polydispersity is small (standard deviation s < 0.08), the phase behavior is essentially unchanged from that observed in monodisperse systems; thus nematic, smectic, and crystal phases are exhibited. For an intermediate range of polydispersities (0.08 < s < 0.18), the smectic phase is found to become increasingly destabilized with respect to the nematic phase at low densities and a columnar phase at high densities. This eventually leads to a terminal polydispersity (s » 0.18) above which the smectic phase is no longer stable. Beyond this value, only nematic and columnar phases are observed.