Alumina interaction with AMPS-MPEG random copolymers I. Adsorption and electrokinetic behavior

Adsorption of brush copolymers, bearing sulfonate groups and polyethylene glycol segments, on to alumina particles in suspension in water has been investigated. Study of the adsorption isotherms revealed that the copolymers displayed a strong affinity for the surface of the alumina regardless of the fraction of ionic groups on the polymer. For poly(ethylene glycol) content greater than 50%, the adsorption isotherms revealed an initial adsorption plateau followed by a second one. The shape of the adsorption isotherms was interpreted in terms of the polymer configuration at the solid-to-liquid interface. The effects of the pH and the ionic force on adsorption were studied and connected to the effects of interaction between chain segments at the surface of the alumina particles. Changes in the electrokinetic properties of the alumina particles after addition of the copolymers were investigated by following the zeta potential of particles as a function of pH. In the presence of the copolymer continuous shift of the isoelectric point IEP to a more acidic values was observed. Beyond a certain concentration the zeta potential remained negative regardless of the pH. (C) 2003 Elsevier Science (USA). All rights reserved.