Unique structure and properties of inorganic-organic hybrid films prepared from acryl/silica nano-composite emulsions

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-co-n-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.