Liquid crystal phase transitions in bidisperse hard-rod systems

The effect of bidispersity on the isotropic-nematic transition is discussed within the framework of Onsager's second-virial theory. The behaviour of bidisperse hard rods beyond the nematic phase is investigated by simulating binary mixtures of hard parallel spherocylinders with different lengths. The behaviour of these mixtures differs markedly, quantitatively as well as qualitatively, from the phase behaviour of the separate monodisperse components. In particular, it is observed that bidispersity favours columnar order over smectic order.