Poly(styrene-co-maleic anhydride) (SMA)/silica and poly(styrene-co-acrylonitrile) (SAN)/silica hybrids were prepared via a sol-gel route by using silicic acid oligomer (SAO) from water glass in this article. This convenient route is different from the traditional one from tetraethoxysilane (TEOS). The polycondensation behavior of the SAO and the aggregation behavior of the silica particles in the hybrids were investigated. The prepared SMA(SAN)/silica hybrids were characterized by infrared spectroscopy, dynamic light scattering, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. The results showed that the particle size of silica in hybrids increased with increasing silica loading and decreased dramatically by adding the coupling agents. The decomposition temperature and the glass-transition temperature of the hybrids were higher than the precursory polymers. The mechanical properties of blends of acrylonitrile-butadiene-styrene copolymers (ABS) resin with the hybrids were also tested and the results indicated that the well-dispersed silica particles in the hybrids indeed reinforced the blends. Some nanocomposites based on ABS were prepared in this way. (C) 2004 Wiley Periodicals, Inc.