Polymer adsorption and its effect on the stability of hydrophobic colloids

Summary As a first step in a study on the interaction between polymers and hydrophobic colloids we investigated in detail the adsorption of polyvinyl alcohol (PVA) on aqueous silver iodide sols. The adsorption is irreversible. Adsorption isotherms are of the highaffinity type. The amount adsorbed increases with molecular weight and with the fraction of acetate groups in the PVA chain. The effective thickness of the adsorbed layer was determined viscosimetrically and independently checked by an electrophoretic method. Double layer studies enabled the determination of the occupancy of the first layer on the surface by polymer segments. It was found that even at maximal coverage with polymer this layer is still about 30% void. The combination of these data enabled the assessment of the polymer segment distribution. It was found that with not too low coverages the distribution isHoeve- like. The distribution, thus obtained reflects itself in the flocculation of AgI sols by PVA.Presented at the 25th Colloid-Meeting in Munich, October 13–15, 1971