Grafting of hyperbranched polyamidoamine (PAMAM) polymer onto ultrafine silica was prepared. First, an initiating site was incorporated into silica surface by treating silica particle with 3-aminopropyltriethoxysilane producing amino functionalized silica. Then grafting of hyperbranched PAMAM was performed by repetitive reactions between Michael addition of silica amino groups to methyl acrylate (MA) and amidation of the resulting terminal methyl ester groups with ethylenediamine (EDA). Excessive amounts of MA and EDA present in each step were removed by a rotary evaporator and dialysis separation, respectively. FT-IR analysis was employed to monitor the propagation of hyperbranched PAMAM on silica which was carried out until reaching the generation of 3.0. The yellowish liquid product was obtained. Amino group content in each generation was determined which was found significantly lower than theoretical value due to unavoidable side reactions. Laser light scattering and SEM results revealed that the particulate agglomerate was disaggregated into finer particle size as hyperbranched PAMAM generation increased. (C) 2008 Wiley Periodicals, Inc.