Phase equilibria of copolymer-monomer mixtures have been modeled on the basis of experimental cloud-point pressure curves for poly(ethene-co-acrylic acid) and for poly(ethene-co-methacrylic acid). The monomer system was ethene. In case of poly(ethene-co-acrylic acid), in addition, ethene-acrylic acid mixtures were used as the solvent. The association term of the PC-SAFT equation of state has been extended to account for the polydispersity of the copolymer samples. For this purpose, two pseudo-components were introduced for each copolymer. The amount and the molecular weight of these components were related to the number and weight averages of the copolymer material, M-n and M-w, respectively. For the strongly hydrogen-bonded systems, the influence on cloud-point pressures of copolymer composition and of molecular weight distribution can be adequately described by PC-SAFT modeling with temperature-independent parameters. (c) 2006 Elsevier B.V. All rights reserved.