GRAFTING OF DENDRIMER-LIKE HIGHLY BRANCHED POLYMER ONTO ULTRAFINE SILICA SURFACE

To modify ultrafine silica surface, the grafting of polyamidoamine den drimer, a new class of topological macro-molecules, onto the silica su rface was investigated, Introduction of amino groups as an initiator s ite on the silica surface was achieved by the treatment of the silica with gamma-aminopropyltriethoxysilane. Polyamidoamine dendrimer was pr opagated from silica surface by repeating two processes: (1) Michael a ddition of methyl acrylate to surface amino groups, and (2) amidation of the resulting eaters with ethylenediamine. The amino group content of the resulting silica increased from 0.40 mmol/g to 8.30 mmol/g afte r 10th generation. In addition, the percentage of grafting increased w ith increasing generation and reached to 575.7% after 10th generation. However, these values were considerably smaller than the theoretical values. This indicates that the propagation of dendrimer grafting from silica surface was not achieved theoretically and 'dendrimer-like' hi ghly branched polymer was grafted onto the surface, because of steric hindrance of grafted dendrimer, The effects of amino group content as an initiator site and reaction conditions on the grafting of the polym er onto silica surface were also investigated. Dendrimer-like highly b ranched polymer grafted ultrafine silicas gave a stable dispersion in a good solvent for the polyamidoamine dendrimer. (C) 1998 Elsevier Sci ence B.V. All rights reserved.