Poly(ethylene oxide) (PEO) with three different salts, ZnCl2, ZnBr2 and ZnI2 has been characterized at various temperatures and compositions by optical microscopy and differential scanning calorimetry. A molecular thermodynamic model based on both an extended Flory-Huggins theory and a Debye-Huckel theory modified by Guggenheim is developed to interpret the liquidus curves in the resulting phase diagram. The proposed model considers not only short-range specific interactions between the salt ions and the polymer or solvating base groups (oxygen in PEG) of the polymer leading to loose complex formation but also long-range electrostatic forces between salt ions. Quantitative description according to the proposed model is in good agreement with experimentally observed transition temperature of a given system including an eutectic point.