ACID-BASE INTERACTIONS IN ADHESION - THE CHARACTERIZATION OF SURFACES AND INTERFACES BY XPS

The consideration of acid-base interactions now plays an important role in the field of adhesion science. In this paper we describe ways in which the surface specificity of XPS can be employed to gauge the acidity or basicity of inorganic and organic surfaces, using a number of novel preparation methods. The methods described rely on the interaction of probe species, in either the gas, liquid or solid phase with the material of interest. For the determination of the properties of inorganic surfaces we describe ways in which the IEPS (isoelectric point of the solid surface) of hydroxylated iron surfaces can be determined by XPS used in conjunction with an ion exchange method. For polymer surfaces we show how the diffusion of Na+ from a soda-lime glass substrate provides an indicator of polymer acidity and illustrate how solvent vapour uptake contains valuable information relating to polymer acidity and acid-base adduct formation. Finally we indicate the manner in which XPS can be used to identify molecular reorientation at the polymer/inorganic interface, which is readily explained in terms of acid-base interactions.