Acid-base Interactions 10.1 GENERAL CONCEPT OF ACID-BASE INTERACTIONS

Acid-base interactions have found numerous applications in research dealing with adsorption of molecules of liquids on the surfaces of solids. The main focus of this research is to estimate the thermodynamic work of adhesion, determine mechanism of interactions, analyze the morphology of interfaces and various surface coatings, develop surface modifiers, study the aggregation of macromolecular materials, explain the kinetics of swelling and drying, understand the absorption of low molecular weight compounds in polymeric matrices, and determine the properties of solid surfaces. In addition to these, there are many other applications. Several techniques are used to determine and interpret acid-base interactions. These include: contact angle, inverse gas chromatography, IGC, Fourier transform infrared, FTIR, and X-ray photoelectron spectroscopy, XPS. These methods, as they are applied to solvents are discussed below. Contact angle measurements have long been used because of common availability of instruments. In recent years, they have been developed from simple optical devices to the present day precise, sophisticated, computer-controlled instruments with sufficient precision. Van Oss and Good developed the basic theory for this method. Their expression for surface free energy is used in the following form: