Interactions of silica nanoparticles with poly(ethylene oxide) and poly(acrylic acid): Effect of the polymer molecular weight and of the surface charge

The properties and the structure of polymer-modified silica nanoparticles were investigated by several characterization methods, with an emphasis on scattering techniques. Both bare and amino functionalized nanoparticles were used. To determine the effect of the charge, the polymer used was either nonionic poly(ethylene oxide) (PEO) or partially deprotonated poly(acrylic acid) (PAA). The particles coated with PEO were investigated by small-angle neutron scattering using the method of external contrast variation to observe the polymer coverage. The quantity adsorbed was found to be increasing with the molecular weight, and the surface type, bare or aminated, did not have a significant influence on the quantity adsorbed. The adsorption of PAA on positively charged aminated particles was investigated by dynamic light scattering and zeta potential measurements. A charge reversal, from positive to negative, was induced by the presence of PAA. Through the derivation of the structure factor, small-angle X-ray scattering provided significant information on the formation of aggregates at low PAA concentrations.

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► Polyethylene oxide was adsorbed on bare and aminated silica nanoparticles.
► Partially deprotonated polyacrylic acid was adsorbed on aminated nanoparticles.
► The amount of polymer adsorbed was determined by neutron scattering.
► The positive charge of the aminated particles was reversed by polyacrylic acid.
► The interactions between the aminated particles were studied by X-ray scattering.