Desorption of Adsorbed Poly(ethylene Oxide) from Colloidal Polystyrene Particles

This paper reports on the use of a polyoxyethylene alkylphenol surfactant to desorb adsorbed poly(ethylene oxide) from the surfaces of colloidal polystyrene particles in aqueous media. Adsorption and desorption were quantified by measurement of polymer solution concentrations before and after surfactant treatment. To do this, two calibration surfaces were developed and verified so that the solution concentrations of polymer and surfactant could be quantified simultaneously. Adsorption isotherms and data from attempts to adsorb polymer onto particles with preadsorbed surfactant suggest that the surfactant should be able to desorb the polymer. However, desorption experiments in which the surfactant attacks preadsorbed polymer layers show that significant desorption occurs only under certain conditions. The effects of starting polymer solution concentration, polymer molecular weight, surfactant concentration, and time on desorption behavior are illustrated. Information on polymer configurations can be inferred from hydrodynamic layer thicknesses obtained through dynamic light scattering. A simple physical picture involving the competition of polymer and surfactant for adsorption sites can rationalize all of the observations.