Ring-opening polymerization of ε-caprolactone and L-lactide from silica nanoparticles surface

Coating of silica nanoparticles by biocompatible and biodegradable polymers of epsilon-caprolactone and L-lactide was performed in situ by ring-opening polymerization of the cyclic monomers with aluminum, yttrium, and tin alkoxides as catalysts. Hydroxyl groups were introduced on the silica surface by grafting of a prehydrolyzed 3-glycidoxypropyl trimethoxysilane to initiate a catalytic polymerization in the presence of metal alkoxides. In this manner, free polymer chains were formed to grafted ones, and the graft density was controlled by the nature of the metal and the alcohol-to-metal ratio. The grafting reaction was extensively characterized by spectroscopic techniques and quantified. Nanocomposites containing up to 96% of polymer were obtained by this technique. (C) 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1976-1984,2004.