Specific interactions in binary blends of ethylene-vinylacetate copolymer (EVA) with various low molecular weight terpene-phenol tackifying resins (TPR) were systematically investigated, as a function of the composition of the blend and of the electron-acceptor ability of the resin, using attenuated total reflection Fourier transform IR (ATR-FTi.r.) spectroscopy. Molecular acid-base complexes (according to Lewis＇ electron acceptor-donor concepts) were evidenced between TPR hydroxyl groups and EVA carbonyl groups. Quantitative information on the fraction of acid-base bonded entities, the enthalpy and the equilibrium constant of pair formation were obtained. It appears that the amorphous phases of such polymer blends remain thermodynamically miscible whatever the composition of the blend and the resin acidity. On the contrary, a crystalline transition of the EVA copolymer is observed, depending on the blend composition and resin acidity. This transition is discussed in terms of enthalpy and entropy considerations based on FTi.r. and differential scanning calorimetry (DSC) investigations. Fundamental results are then summarized in order to predict the melting enthalpy of a polymer blend.