In this Study, grafting of hyperbranched polyamidoamine (PAMAM) polymer onto Ultrafine silica followed by functionalization via the introduction of phosphonic acid groups into the branch ends was performed. First, an initiating site was incorporated into the silica surface by reacting the silica silanol group with 3-aminopropyltriethoxysilane, producing amino-functionalized silica. The free amine group content was altered by varying the ratio of methanol to water in the hydrolysis step of the silanization reaction. Grafting of PAMAM was attained by three rounds of sequential Michael addition of silica amine groups to methyl acrylate and amidation of the resulting terminal methyl ester groups with ethylenediamine. Completion of the grafting reaction in each step was clearly confirmed using FTIR analysis. Excessive ethylenediamine and unattached hyperbranched PAMAM present in the reaction product were removed by dialysis with a molecular weight cutoff of 6000-7000 Daltons. However, the amino group content determined in each step was found to be significantly lower than theoretically expected, perhaps indicative of side reactions and, in later stages, steric hindrance. The resultant hyperbranched PAMAM-grafted onto silica was functionalized by phosphorylation of the terminal amino groups by a Mannich type reaction, producing the phosphorylated hyperbranched PAMAM-grafted silica. Then its application on cotton fabric to produce fire-retardant cellulose was tentatively investigated. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3336-3347,2008