Dynamics of glassy polymer melts in confined geometry: A Monte Carlo simulation

Dynamic properties of a dense polymer melt confined between two hard walls are investigated over a wide range of temperatures by dynamic Monte Carlo simulation. The temperature interval ranges from the ordinary Liquid to the strongly supercooled melt. The influence of temperature, density and confinement on the polymer dynamics is studied by various mean-square displacements, structural relaxation functions and quantities derived from them (relaxation times, apparent diffusion coefficients, monomer relaxation rates), yielding the following results: The motion of the monomers and polymers close to the walls is enhanced in parallel, but reduced in perpendicular direction. This dynamic anisotropy strongly increases during supercooling and extends into the bulklike inner region of the film over a length scale which is larger than the bulk radius of gyration at low temperatures. However, the absolute freezing of the melt occurs in each layer at the same temperature for both the parallel and the perpendicular direction.