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 amino 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 fireretardant cellulose was tentatively investigated.

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.