Diffusion of small particles in a solid polymeric medium

摘要

We analyze diffusion of small particles in a solid polymeric medium takinginto account a short range particle-polymer interaction. The system is modeledby a particle diffusion on a ternary lattice where the sites occupied bypolymer segments are blocked, the ones forming the hull of the chainscorrespond to the places at which the interaction takes place, and the rest arevoids, in which the diffusion is free. In the absence of interaction thediffusion coefficient shows only a weak dependence on the polymer chain lengthand its behavior strongly resembles usual site percolation. In presence ofinteractions the diffusion coefficient (and especially its temperaturedependence) shows a non-trivial behavior depending on the sign of interactionand on whether the voids and the hulls of the chains percolate or not. Thetemperature dependence may be Arrhenius-like or strongly non-Arrhenius,depending on parameters. The analytical results obtained within the effectivemedium approximation are in qualitative agreement with those of Monte Carlosimulations.