We have recently proposed a compressible lattice model for CO2 + polymer systems in which CO2 forms complexes with one or more functional groups in the polymer. Furthermore, we have shown that this model is able to simultaneously correlate phase equilibria, sorption behavior, and glass transition temperatures in such systems. In the present work, we extend the model to ternary CO2 + cosolvent + polymer systems and demonstrate that cloud point behavior in CO2 + dimethyl ether + poly (epsilon-caprolactone), CO2 + dimethyl ether + poly (isopropyl acrylate), and CO2 + dimethyl ether + poly (isodecyl acrylate) systems can be predicted using parameters obtained from binary data. Our results also suggest that dimethyl ether may form weak complexes with poly (epsilon-caprolactone), poly (isopropyl acrylate), and poly (isodecyl acrylate). (C) 2010 Elsevier B.V. All rights reserved.