Adhesive forces between adsorbed anionic polyelectrolyte layers in high ionic strength solutions

Abstract

Direct interaction forces between a hematite surface and a silica sphere in the presence of high-molecular weight anionic polyelectrolytes, sodium polyacrylate (NaPAA), an acrylamide/acrylate copolymer, an hydroxamate copolymer and starch have been measured using the atomic force microscope (AFM). In aqueous solution at high pH, the interaction between the bare oxide surfaces is well described by DLVO theory and is dominated by a repulsive electrostatic force. Addition of a high-molecular weight polyelectrolyte did not significantly alter the forces on approach. There was no sign of steric repulsion prior to the distance of closest approach. Therefore, it appears that these molecules are ads..