PUB - Publikationen an der Universität Bielefeld

Molecular dynamics (MD) simulations in the canonical (NVT) and the isothermal-isobaric (NPT) ensemble using COMPASS III molecular force fields were performed to study the penetrant diffusion of water (H₂O), hydrogen peroxide (H₂O₂) and oxygen (O₂) in isotactic polypropylene (iPP) and hydrogen (H₂) in iPP and atactic polypropylene (aPP) for time intervals up to 11 ns and in the case of H₂O₂up to 22 ns. We found robust cluster formation in the case of H₂O and H₂O₂. Further, the diffusion coefficients for all these systems were estimated by mean-square displacement analysis. Our results are consistent with previously published experimental and computational data except for the diffusion of H₂in polypropylene where our results are one and two orders of magnitude higher, respectively. Grand Canonical Monte Carlo (GCMC) simulations were used to determine the sorption loading and saturation concentration of H₂O, O₂and H₂in iPP, where we find good agreement for H₂O with experimental results. By means of MD simulation the glass transition temperature (T_g) of iPP was estimated to 273.66 ± 4.21 K which is consistent with previously published experimental results.