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Nanocomposite particles consisting of silica (inorganic core) and polyacrylate (organic shell) were prepared in a form of emulsion by a new and simple methodthe emulsion polymerization of acrylic monomers in the presence of silica sol. The key technique of the present emulsion polymerization, which made the formation of the nanocomposites successful, is the usage of nonionic surfactant above its cloud point. The morphology of the composite was investigated by DLS, AFM, and TEM, which clearly showed formation of the core-shell-type particles. A transparent film was prepared by casting the emulsion, which showed high resistibility against organic solvents.

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Transparent films were prepared from nano-composite emulsions, which contained nano-size core-shell-type particles (ca. 60 nm in diameter) consisting of colloidal silica (inorganic core, ca. 30 nm in diameter) and poly(methyl methacrylate-con -butyl acrylate) (organic shell). The silica content in the film could be increased up to 150 wt/wt% by keeping its homogeneity. It was revealed that the formation of such a core-shell structure is guided by the surface sedimentation of a nonionic surfactant above its clouding point to form an organic thin layer that can provide the sites for monomer absorption and polymerization. The thermal and mechanical properties of the resultant nano-composite films were evaluated by various methods and compared with those of simple blend films of the corresponding acrylic emulsion and colloidal silica. It was clarified that the high-temperature resistance of the nano-composite films can be improved by the reinforcement effect of silica particles.