Abstract: Polymer-modified silica sols were synthesized by the ammonia-catalyzed hydrolysis of tetraethoxysilane with polyvinylpyrrolidone (PVP) as polymer modifier in methyl alcohol. By small angle X-ray scattering (SAXS), the microstructure was studied with the assistance of dynamic light scattering (DLS). The dependence of the particle size distribution, fractal characteristics, and the rheology of PVP-modified silica sols on the PVP content, ammonia content and water content in sols was analyzed. It is easy to form hydrogen bonds between the surface hydroxyls of silica particles and the negatively charged oxygen atoms of inner amide in PVP molecules, and this holds back the further growth of silica particles. Thus the gelation was retarded and the rheology of the sol was largely modified by PVP.

Key words: Sol, Silica, Small angle X-ray scattering, Rheology