Hierarchical modeling of polymer permeation

To describe polymer permeation of penetrants in polymer melts one typically looks at two quantities: The diffusivity and the solubility of the penetrant.

We use a hierarchical modeling approach to study the permeation of ethylbenzene (EB) in molten atactic polystyrene (PS). This is a great industrial interest since PS is a widely used plastic material. Diffusion coefficients and excess chemical potentials of EB in PS are calculated to study the permeation of EB in PS. Therefore we perform molecular dynamics (MD) simulation of penetrant diffusion on a coarse grained (CG) as well as on an atomistic level. Time mapping allows us to predict permeation data. Via inverse mapping of well equilibrated CG melts atomistic structures are generated to perform nonequilibrium free energy calculations to calculate penetrant excess chemical potentials.

The picture shows a simulation of ethylbenzene in a polystyrene melt.

D. Fritz, C. R. Herbers, K. Kremer, N. F. A. van der Vegt, Soft Matter, 5, 4556-4563 (2009).