nitroxide-mediated radical polymerization of styrene initiated from the surface of titanium oxide nanoparticles

titanium dioxide (tio2) nanoparticles, with an average size of about 45 nm, were encapsulated by polystyrene using in situ nitroxide mediated radical polymerization   in the presence of 3-aminopropyl triethoxy silane (aptes) as a coupling agent and 2, 2, 6, 6-tetramethylpiperidinyl-1-oxy  as a initiator. first, the initiator for nmrp was covalently bonded onto the surface of titanium dioxide nanoparticles through our novel method. for this purpose, the surface of tio2 nanoparticle was treated with 3-aminopropyl triethoxy silane, a silane coupling agent, and then these functionalized nanoparticles was reacted with ±-chloro phenyl acetyl chloride. the chlorine groups were converted to nitroxide mediated groups by coupling with 1-hydroxy-2, 2, 6, 6-tetramethyl piperidine. these modified tio2 nanoparticles were then dispersed in styrene (st) monomers to carry out the in situ free radical polymerization.