We report the coating of maghemite (␥-Fe 2 O 3 ) nanoparticles with poly(caprolactone) (PCL) through a covalent grafting to technique. -Hydroxy-PCL was first synthesized by the ring-opening polymerization of -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 mol of polymer chains per m 2 of maghemite surface were obtained with this grafting to technique.
Summary: A methacrylate‐functionalized poly(ethylene glycol) macromonomer was copolymerized at the surface of methacrylate‐derivatized maghemite nanoparticles. After silylation of the magnetic core with methacryloxypropyltrimethoxysilane, two grafting procedures based on either a direct copolymerization reaction in water or an inverse emulsion polymerization were compared. A direct copolymerization led to low polymer surface amounts, whereas an inverse emulsion process allowed nanocomposite particles containing up to 90 wt.‐% polymer to be obtained.TEM picture of maghemite‐PEG hybrid particles.magnified imageTEM picture of maghemite‐PEG hybrid particles.
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