Organic-inorganic hybrid hydrogels based on linear poly(N-vinylpyrrolidone) and products of hydrolytic polycondensation of tetramethoxysilane

The initial stage of gelation of organic-inorganic hybrid hydrogels based on poly(N-vinylpyrrolidone) and the products of hydrolytic polycondensation of tetramethoxysilane has been studied by capillary viscometry. The development of strong bonds between polymer molecules and silica particles in aqueous solutions is proved by the electrokinetic sonic amplitude method. The molecular mass of poly(N-vinylpyrrolidone), the concentration of starting components, and their total amount affect the onset time of gelation in poly(N-vinylpyrrolidone)—water—tetramethoxysilane systems. The general scheme of formation of three-dimensional networks in such systems under the conditions of mutual penetration of poly(N-vinylpyrrolidone) coils is suggested. According to this scheme, nanoparticles of the general formula SiO _x (OH) _y (OR) _z linking poly(N-vinylpyrrolidone) macromolecules serve as junctions of the gel network due to the formation of hydrogen bonds between hydrogens of silanol groups of organosilanes and oxygens of carbonyl groups of poly(N-vinylpyrrolidone).