Ion diffusion in a polymer network: Monte Carlo studies and the dynamic percolation approach

An athermal lattice model for diffusion of tracer particles through a network of polymer chains with variable length is studied (i) by Monte Carlo simulation and (ii) by a more coarse-grained description in terms of dynamic percolation (DP) theory. A recently developed fluctuation site-bond Monte Carlo algorithm is used that allows us to investigate systems with high monomer density. In the high-density regime we find that the tracer correlation factor becomes much smaller than unity, and the time-dependent diffusion coefficient of tracer particles develops power-law behavior. DP-results for diffusion, which require much less computational effort, compare favorably with the full simulations up to moderate densities. Limitations of the DP-concept for high densities are demonstrated.