ADSORPTION OF NONIONIC AND CATIONIC POLYMERS ON SILICA FROM THEIR MIXED AQUEOUS-SOLUTIONS

The adsorption of polyvinylpyrrolidone (PVP) and poly(dimethyldiallylammonium chloride) (PDC) on silica from their mixed aqueous solutions has been investigated as a function of PVP concentration in the presence of PDC. The adsorption of PVP is almost unchanged with the feed concentration of PVP, while the adsorption of PDC decreases with increasing PVP concentration, especially at high concentrations of PDC. The conformation of PVP in the adsorbed layer on silica is relatively flat at low concentrations of PDC, but is extended in solution at high concentrations of PDC. The stability of the silica dispersion is low and the xi potential is relatively small at low concentrations of PDC, whereas a stable dispersion is obtained at high concentrations of PDC and the xi potential is large. Thus the stability of the dispersion is well correlated with the electrostatic repulsion and steric repulsion forces operating at the particles.