ADSORPTION OF WEAK POLYELECTROLYTES ON HIGHLY CHARGED SURFACES - POLY(ACRYLIC ACID) ON POLYSTYRENE LATEX WITH STRONG CATIONIC GROUPS

We have studied the adsorption of the weak polyelectrolyte poly(acrylic acid) (PAA) on a positively charged polystyrene latex. The latex surface contained quaternary ammonium groups, so that the surface charge was independent of pH. Hence, when the pH was changed, only the degree of dissociation of the polymer varied. We found that the adsorbed amount is low at high pH, where PAA is fully charged. With decreasing pH the adsorption increases and passes through a maximum at about 1 pH unit below the intrinsic dissociation constant pK0 of the carboxylic groups of the macromolecule. The ionic strength has little effect. The experimental results agree very well with a recent extension of the model of Scheutjens and Fleer to polyelectrolyte adsorption. © 1990, American Chemical Society. All rights reserved.