Modeling Solubility and Interfacial Properties of Carbon Dioxide Dissolved in Polymers

A classical density functional theory approach has been applied to evaluate the solubility and interfacial properties of CO2 dissolved in poly(methyl methacrylate) (PMMA) and polystyrene (PS) matrices quantitatively. Apart from the free-energy functional for hard-sphere reference given by the fundamental measure theory, a weighted free-energy functional for attractive dispersion and the contributions of chain connectivity and conformation have been integrated into the theoretical model to improve its predictive capability. The force-field parameters are cited from the literature, except that the Lennard-Jones potentials of sites are regressed to reproduce the experimental gas–liquid phase equilibria of pure PMMA and PS. It is shown that, in the two systems, the current model provides reliable predictive results of solubilities, swelling ratios, and interfacial tensions, which are particularly important in the bubble nucleation during polymer foaming.