Temperature effect on the adsorption equilibrium at the silica–polyethylene glycol solution interface

The influence of temperature in the range 15–35 °C on polyethylene glycol (PEG) adsorption on the silica (SiO2) surface was examined. For this purpose the following methods were applied: spectrophotometry, viscosimetry and potentiometric titrations. They allow determination of polymer adsorbed amounts, its adsorption layer thickness and surface charge density of the solid with the adsorbed PEG. Moreover, viscosity measurements enabled characteristics of macromolecules conformation in the solution, whereas the adsorption experiments – calculation of the Gibbs energy of polymer adsorption. The obtained results indicate that temperature influences the structure of polymer adsorption layer. The temperature rise causes polymer coils developing which results in: the increase of polymer adsorption, its adsorption Gibbs energy, as well as the increase of linear dimensions of PEG chains in the solution and the formation of thicker adsorption layer of the polymer on the solid surface.