Effects of ferrocenyl group on refractive index of colloidal crystal system formed by polymer-grafted silica in organic solvent

Colloidal crystallization of copolymer-grafted silica containing ferrocenyl groups in organic solvents and effects of ferrocenyl groups on effective refractive index of colloidal crystal systems were investigated. Poly(ferrocenyl metharylate (FeMA)-co-methyl methacrylate (MMA)-grafted silica gave colloidal crystallization in dimethylformamide and acetonitrile. The colloidal crystals exhibited characteristic coloration due to cooperative effects of specific absorption at 400-500 nm by ferrocenyl group and transmission of 700-800-nm light through the crystals. It was observed that effective refractive index of colloidal crystals systems of poly(FeMA-co-MMA)-grafted silica was higher than that of poly(MMA)-grafted silica. Normalized effective refractive index of the system linearly increased with mole fraction of FeMA in grafted copolymer. However, poly(FeMA-block-MMA) did not bring effective increase of the index because of bias formation of ferrocenyl group on silica.