The present paper describes a versatile route to modify and stabilize ceria nanoparticles with a radical initiator, 4,4′-azobis(4-cyanovaleric acid) (ACVA), allowing a strong interface to be formed via grafting of polymers from the surface. This leads to the successful encapsulation of cerium oxide nanoparticles in a poly(methyl methacrylate) matrix. The interaction between the radical initiator and the surface of ceria is studied by FTIR spectroscopy where a consistent shift of the carboxylate band unequivocally demonstrates that the carboxylate groups of this acidic initiatorcomplex the cerium ions on the ceria surface by means of strong and stable ionic bonding.