The synthesis and characterization of the vinyltriethoxysilane-modified silica nanoparticles were investigated. It was shown that the vinyltriethoxysilane molecules had been successfully grafted onto the silica nanoparticles. The native and silane-modified silica dispersions in N-methyl-2-pyrrolidone with the total solids contents within the range 1-6 wt % exhibited dramatically different flow behaviors. The polymerization of NN'-bismaleimide-4,4'-diphenylmethane (BMI) initiated by barbituric acid in the presence of the native or vinyltriethoxysilane-modified silica nanoparticles were then carried out in gamma-butyrolactone (total solids content = 20%). The higher the level of silica, the better the thermal stability of the BMI/silane/silica composite particles. The silane-modified silica particles significantly improved their dispersion capability within the continuous BMI oligomer matrix. Furthermore, the degree of dispersion of the vinyltriethoxysilane-modified silica particles in the BMI oligomer matrix decreased with the weight percentage of silica based on total solids increased from 20 to 40 wt %. (c) 2006 Wiley Periodicals, Inc.