Microcalorimetry and ellipsometry in surfactant adsorption studies

The applications of calorimetric and ellipsometric methods to the understanding of adsorption phenomena occurring at the solid/liquid interface are presented. Gas adsorption calorimetry and immersion calorimetry can be used to characterise powdered adsorbents in terms of surface area, surface energy and pore size distribution, whereas adsorption from solution calorimetry is well suited to follow in situ the building steps of the surfactant adsorbed layer. On the other hand, ellipsometry allows the adsorption isotherms as well as the thickness of the adsorbed layer to be determined on well defined flat surfaces. Some applications for surfactant studies are reviewed and a recent result, obtained in the case of the adsorption of a cationic surfactant below its Kraft temperature onto silica, is presented.