COMPUTER-SIMULATION STUDIES OF A MODEL SYSTEM FOR LIQUID-CRYSTALS CONSISTING OF SEMIFLEXIBLE MOLECULES

A simple steric model of so-called rfr (rigid-flexible-rigid) molecule s is developed. It consists of two rigid spherocylindrical fragments l inked by a flexible alkyl chain. Molecular dynamics simulations of 128 model molecules are carried out in a periodic box, and the influence of density and alkyl chain length on the molecular order and the self- diffusion is studied. Different liquid crystalline phases are found wh ich an stable within the time scale of the simulations. In agreement w ith experimental results the nematic order parameters and the stabilit y of the phase, as indicated by the location of the isotropic/liquid c rystalline phase transition, show an odd-even effect with respect to t he number of methylene groups in the alkyl chain. A separation of rigi d and flexible fragments is observed leading to smectic liquid crystal line phases.