Hierarchical modeling of polymer permeation

We propose a hierarchical modeling approach for calculating diffusion coefficients and excess chemical potentials of large (non-gaseous) penetrants in polymer melts. The sequence of procedures described in this work includes accelerated, coarse grained molecular dynamics simulations of penetrant diffusion, inverse mapping of coarse grained melt structures, and application of nonequilibrium free energy calculations to determining penetrant excess chemical potentials in well-relaxed atomistic melt configurations. Based on the application to ethylbenzene permeation in polystyrene melts, we discuss how the use of hierarchical models leads to a computationally efficient prediction of permeation data in quantitative agreement with experiments. The procedures outlined in this paper may find future application in modeling permeation in complex, soft matter systems.