Electrostatic properties of polyelectrolyte modified surfaces studied by direct force measurement

Abstract

The interactions between silica and mica surfaces bearing an adsorbed cationic polyelectrolyte, a highly quaternarized poly(2-vinyl pyridine), have been measured using an atomic force microscope with tips modified to incorporate a silica colloid probe. The interactions exhibit classical DLVO behavior, with no steric component detectable at low electrolyte concentration. The diffuse layer potentials of these "composite" interfaces appears to be a function of both the adsorbed layer and underlying surface charge. The point of zero charge of the surfaces differs greatly from the isoelectric point of the unmodified surface, but trends in pH versus surface potential behavior are similar. Diffuse ..