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.　©　2011.