Acid-base theory of adhesion: A critical review

The great importance of acid-base interactions has led to the developement of many models and methods to determine and compare the acid-base behaviour of materials. In spite of its importance, however, the assessment of acid-base properties appears to be a nontrivial and troublesome task, since it requires the determination of the free energy or enthalpy changes induced by the acid-base interactions of the material with some reference chemical species. This review summarizes the main contributions to such an important field of physical chemistry, focussing on their strengths and weaknesses and their correct application in conjunction with the appropriate measurement techniques, encompassing Contact Angle Measurements, Inverse Gas Chromatography (IGC), Immersion Calorimetry, and Atomic Force Microscopy (AFM). Particular attention is paid to van Oss, Chaudhury and Good acid-base theory and contact angle measurements. As an overall conclusion, it is apparent that the various models and techniques, if appropriately applied, can provide extremely valuable informations about the acid-base behaviour of various materials. Nevertheless, a general feeling persists that the different approaches proposed in the literature are not yet satisfactorily consistent nor their findings, although very significant and useful, easy to compare.