FLEXIBLE POLYMERS IN A NEMATIC MEDIUM - A MONTE-CARLO SIMULATION

Monte Carlo simulations of self-avoiding random walks surrounded by al igned rods on a square lattice and a simple cubic lattice were perform ed to address the topological constraints involved for dilute solution s of flexible polymers in a highly oriented nematic solvent. The nemat ic constraint exerted by the solvent is modelled by requiring that the distance between nearest neighbour chain segments in the direction of the director of the nematic solvent is such that a discrete number of rods, representing the perfectly ordered nematic solvent, fits exactl y in between. Rod lengths of one or two lattice spacings are used. In this case interesting scaling behaviour for the radius of gyration and the end-to-end distance is found. Perpendicular to the director the c oil behaves as a two- (or one- in the case of a square lattice) dimens ional self-avoiding walk, whereas parallel to the director it behaves as a random walk. The conformations have a disk-like shape with the ra dius of gyration perpendicular to the director being considerably larg er than the parallel component. These simulations address only one asp ect of flexible polymers in nematic solvents. In reality the presence of the coil also reduces the entropy of the solvent which has exactly the opposite effect on the shape of the polymer coil.