In this study, multifunctional nanoparticles containing thermosensitive polymers grafted onto the surfaces of 6-nm monodisperse Fe3O4 magnetic nanoparticles coated by silica were synthesized using reverse microemulsions and free radical polymerization. The magnetic properties Of SiO2/Fe3O4 nanoparticles show superparamagnetic behavior. Thermosensitive PNIPAM (poly(N-isopropylacrylamide)) was then grafted onto the surfaces Of SiO2/Fe3O4 nanoparticles, generating thermosensitive and magnetic properties of nanocomposites. The sizes of fabricated nanoparticies with core-shell structure are controlled at about 30 nm and each nanoparticle contains only one monodisperse Fe3O4 core. For thermosensitivity analysis, the phase transition temperatures of multifunctioral nanoparticles measured using DSC was at around 34-36 degrees C. The magnetic characteristics of these multifunctional nanoparticles were also superparamagnetic. (C) 2008 Elsevier Inc. All rights reserved.