We report the coating of maghemite (gamma-Fe2O3,) nanoparticles with poly(epsilon-caprolactone) (PCL) through a covalent grafting to technique. omega-Hydroxy-PCL was first synthesized by the ring-opening polymerization of E-caprolactone with aluminum isopropoxide and benzyl alcohol as a catalytic system. The hydroxy end groups of PCL were then derivatized with 3-isocyanatopropyltriethoxysilane in the presence of tetraoctyltin. The triethoxysilane-functionalized PCL macromolecules were finally allowed to react on the surface of maghemite nanoparticles. The composite nanoparticles were characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Effects of the polymer molar mass and concentration on the amount of polymer grafted to the surface were investigated. Typical grafting densities up to 3 mumol of polymer chains per m(2) of maghemite surface were obtained with this grafting to technique. (C) 2004 Wiley Periodicals, Inc.