Functionally modified silica nanoparticles were synthesized by a one-step method, based on the hydrolysis of tetraethyl orthosilicate in aqueous alcohol solutions with the addition of 3-methacryloyloxypropyl trimethoxy silane. The effects of the surfactant, water and ammonia concentration, and reaction temperature on the morphology and particles' size of silica were studied. The particles' size and size distribution of silica were characterized using transmission electron microscopy, scanning electron microscopy and dynamic light scattering. Monodisperse, spherical, functional silica nanoparticles were obtained at the optimal conditions. Afterwards, silica nanoparticles were dispersed in polyurethane (PU) coatings via solution blending to reinforce PU. The thermal and mechanical properties of PU films were measured by thermogravimetric analysis and universal testing machine, respectively. The results showed that the thermal and mechanical properties of PU films were improved with the addition of the modified silica nanoparticles. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.