Characterization of solids and surface modifications by surfactants and polymers.

Probe molecules are used to characterize Lewis-type and Brϕnsted-type surface sites of solids. The number and strength of surface sites are determined by Langmuir adsorption isotherms and by acid-base titrations. The appearance of charged surface sites is determined by dissolution experiments and the overall surface energy by immersion experiments. First-order standard thermodynamic properties (Gibbs energies, enthalpies and entropies) are used to characterize the state of probe molecules in solution and the interaction between probe molecules and surface sites. The state of surfactants in solution is characterized using regular solution model. The adsorption to surface sites is quantified by Langmuir isotherms. Their self-assembly at surface sites is initiated at somewhat lower concentration as compared to micelle formation in solution. Loosely bound surfactants and (hemi)micelles follow the prediction of Henry adsorption isotherm. Solution properties of polymers are evaluated by applying total (Scatchard-Hildebrand, Flory-Huggins) combinatory energy. A diminished solubility results in adsorption. Polymer adsorption can be characterized using Freudlich adsorption isotherm and predicted using solubility spheres. The observations are discussed in terms of preferential solid-adsorbent (probe, surfactant, polymer), adsorbent-liquid (solubility) or solid-liquid (wetting) interactions.