Dynamics of polymeric layer structures

Abstract The method of Brownian dynamics has been used for the computer modelling of the motion of a two-dimensional model of rotors that simulates the properties of layer structures that exist in certain types of polyimides, smectic liquid crystals and polycarbonates; the equilibrium and dynamic properties of the system have been determined. As the temperature is lowered, the system undergoes a transition from a disordered to an ordered state with the rotors packed in a “parquet-floor” fashion (a second-order phase transition). The rotational diffusion of the rotors over a wide temperature range has been studied. At low temperatures ( T g ) the rotors principally execute tortional-vibrational movements close to the equilibrium values. Close to T g , the motion of the rotors is represented by small angular displacements around the equilibrium positions and by jumps through an effective potential barrier that is determined by the interaction with a mobile environment. The dependence of the mean potential energy of a rotor on the orientational angle was determined from the numerical experiment. The motion of an individual rotor in the multi-particle system modelled is found to approximate to that of a separate rotor in this mean potential.