Methane adsorption in PIM-1

We report the results of Grand Canonical Monte Carlo (GCMC) simulations of methane adsorption in a prototypical polymer of intrinsic microporosity, PIM-1. Polymer chains were represented with a united-atom model, with Lennard-Jones parameters obtained from the TraPPE potential. Additionally, partial charges were calculated from ab initio methods using Gaussian (HF/6-31G ^* basis set). Samples of PIM-1 were built at low density conditions, followed by a Molecular Dynamics compression protocol until densities of 1.2 g∈cm^-3 were achieved. This protocol proved to be suitable for the realistic modeling of the amorphous structure of PIM-1. Surface areas and pore size distributions were measured and compared to available experimental data. The simulated pore size distribution present a peak at 4.3 Å, consistent with experimental results. GCMC simulations of methane adsorption were performed, and found to qualitatively reproduce the shape of the available experimental isotherm.