The novel predictive approach of Partial Solvation Parameters (PSP) is extended and applied to polymer mixtures. Quantum mechanics and statistical thermodynamics are used in order to extract information on the molecular descriptors of each compound and develop simple analytical expressions for all basic thermodynamic quantities of mixtures. Emphasis is given on hydrogen-bonded polymer mixtures. Apart from polymer polymer miscibility, the PSP approach is used for the prediction of melting point depression, fraction of hydrogen-bonded groups, critical composition of a copolymer for miscibility with another polymer, and the Flory-Huggins chi(123) interaction parameter of a solute-probe (I) at infinite dilution in a mixture of polymers (2,3) which is obtained from inverse gas chromatography (IGC) experiments. The predictions are compared with experimental data and the agreement is critically discussed. The predictions of polymer polymer miscibility on the basis of spinodal lines are compared with the corresponding predictions on the basis of chi interaction parameters. The strength and weakness of the approach are also critically discussed in relation with its capacity and reliability to act as a designing tool of new compatible polymer blends. The perspectives of this unified approach to solution thermodynamics are discussed. (C) 2013 Elsevier Ltd. All rights reserved.