The Cahn-Hilliard theory was combined with equations of state (the original statistical associating fluid theory, the perturbed-chain statistical associating fluid theory or the Sanchez-Lacombe lattice theory) in order to describe both the solubility of carbon dioxide in polystyrene and the interfacial properties between the liquid mixture and the pure gas phase. The comparison between the predicted interfacial tensions and the experimental data from the literature is discussed. (c) 2004 Elsevier B.V. All rights reserved.