In this work the electrolyte perturbed chain statistical associating fluid theory (ePC-SAFT) was applied to model aqueous two-phase systems (ATPS) containing combinations of polyethylene glycol dimethyl ether (PEGDME), polypropylene glycol (PPG) and three poly(ethylene glycol-co-propylene glycol) copolymers in combination with 12 different inorganic salts for temperatures ranging from 278 K to 333 K. For the polymer modeling, a copolymer approach was applied splitting the polymer in different segment types accounting for their different molecular interactions. Using this approach allows for quantitative modeling of phase properties of aqueous homopolymer and copolymer solutions. ATPS consisting of water, salt and one out of the five polymers were successfully modeled by using only one binary interaction parameter between each polymer segment type and each ion. Applying these parameter set, the influence of (co)polymer composition, polymer molecular weight, and temperature on the phase composition and phase densities could be modeled accurately. (C) 2014 Elsevier B.V. All rights reserved.