Influence of water-soluble nonionic polymers adsorption on colloidal properties of nanosilica dispersions

The relationships between the adsorption of poly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO), and poly(vinyl pyrrolidone) (PVP) of various molecular weights onto nanosilica and the stability and rheological properties of the aqueous dispersions were analyzed. The adsorption isotherms for the polymers correspond to the Langmuir-type isotherms. The adsorption maximum slightly increases with increasing molecular weight of the polymers. The sedimentation and aggregative stability of the silica dispersion decreased at a low amount of an adsorbed polymer (less than a monolayer). At this polymer content, a significant increase in the viscosity of dispersions is observed due to the formation of polymeric bridges between silica nanoparticles from neighboring aggregates of them. If the amount of adsorbed polymer exceeds the monolayer then the stabilizing effect is observed due to the steric factor preventing the bridge formation and the viscosity of dispersion decreases slightly compared with systems with a low polymer content.