Phosphonic Acid Functionalization of Hyperbranched Polyamidoamine Grafted Ultrafine Silica to Prepare the Flame Retardant for Cotton Fabric
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Grafting of hyperbranched polyamidoamine (PAMAM) dendrimer onto ultrafine silica followed by the introduction of phosphonic acid groups onto branch ends was carried out. First, an initiating site was incorporated into silica surface by reacting the silica silanol group with 3-aminopropyltriethoxysilane, producing amino-functionalized silica. The free amine group content was controlled by varying ratios of methanol to water in the hydrolysis step of sol-gel reaction. Then grafting of PAMAM was performed by repetitive reactions between Michael addition of silica amino groups to methyl acrylate and amidation of the resulting terminal methyl ester groups with ethylenediamine. Amino group content in each generation was determined. This was found to be significantly lower than theoretical value due to unavoidable side reactions. After the G3.0 hyperbranched PAMAM grafted onto silica was synthesized, phosphonic acids functionalization of the terminal amino groups by the Mannich type reaction was carried out. The phosphorylated hyperbranched PAMAM grafted silica was achieved and its application on cotton fabric to produce phosphonated cellulose was studied.