1. Acid-base interactions determine adsorption and bonding of polymers to fillers. 2. Quantitative predictability of the enthalpy of such bonding is attainable from the Drago C and E equation once the C and E constants are determined for polymers and fillers. 3. Infrared and calorimetric methods are discussed for determining the C and E constants for polymers and fillers. 4. For the case of poly(methylmethacrylate) filled with silica, the enthalpy of bonding has been determined by FTIR spectroscopy. 5. Acid-base interactions between polymers and fillers generate high zeta-potentials which tend to eliminate filler flocculation and reduce viscosity of filled polymer melts.