Cerium oxide encapsulation by emulsion polymerization using hydrophilic macroRAFT agents

Composite organic/inorganic latexes encapsulating CeO2 nanoparticles were successfully synthesized by surfactant-free emulsion polymerization. Since carboxylic acid groups are known to interact strongly with the surface of CeO2, either a poly(acrylic acid) (PAA) homopolymer or a random copolymer of acrylic acid (AA) and n-butyl acrylate (BA) was first synthesized in solution using trithiocarbonate compounds as RAFT agents. The interaction between the resulting macroRAFT agents and the surface of CeO2 nanoparticles was investigated by the study of the adsorption isotherms. The dispersion state of the resulting CeO2 nanoparticles coated with macroRAFT agents was characterized by DLS and SAXS measurements. The two types of macroRAFT agent-coated CeO2 nanoparticles were then used in the emulsion polymerization of hydrophobic monomer(s) (BA alone or a mixture of methyl methacrylate (MMA) and BA) in order to form the encapsulating shell. The morphology of the nanocomposite latex particles was characterized by (cryo-)TEM and correlated with the surface modification and the experimental conditions. CeO2 nanoparticles were efficiently encapsulated in the core of poly(MMA-co-BA) latex particles when poly(AA-co-BA) macroRAFT agents were first adsorbed onto the CeO2 surface.