Molecular dynamics of model liquid crystals composed of semiflexible molecules

Results of molecular-dynamics computer simulations are presented for a simple microscopic model of thermotropic liquid crystals. The system is composed of short multibead semiflexible chains where the beads are connected by an anharmonic spring. The intermolecular bead-bead interactions are modeled by Lennard-Jones potentials, the attractive part is taken into account only between the stiff parts. Heating the system, solid, smectic-A, and liquid phases are found. For the symmetric molecules and anisotropic potentials studied first, the smectic-A phase is clearly defined over a wide range of temperatures, whereas the nematic phase is not present or too narrow in temperature to be seen clearly. The evolution of the systems has also been studied as a function of the length of flexible parts and the strength of the stiff-stiff potential. {} 1996 The American Physical Society.