Diffusion of Small Particles in Polymer Films

The motion of small probe molecules in a two-dimensional system containing frozen polymer chainswas studied by means of Monte Carlo simulations. The model macromolecules were coarse-grainedand restricted to vertices of a triangular lattice. The cooperative motion algorithm was used to generaterepresentative configurations of macromolecular systems of different polymer concentrations. Theremaining unoccupied lattice sites of the system were filled with small molecules. The structure ofthe polymer film, especially near the percolation threshold, was determined. The dynamic lattice liquidalgorithm was then employed for studies of the dynamics of small objects in the polymer matrix. Theinfluence of chain length and polymer concentration on the mobility and the character of motion ofsmall molecules were studied. Short- and long-time dynamic behaviors of solvent molecules werealso described. Conditions of anomalous diffusions’ appearance in such systems are discussed. Theinfluence of the structure of the matrix of obstacles on the molecular transport was discussed.