Grafting of ‘dendrimer-like’ highly branched polymer onto ultrafine silica surface

Abstract

To modify ultrafine silica surface, the grafting of polyamidoamine dendrimer, a new class of topological macromolecules, onto the silica surface was investigated. Introduction of amino groups as an initiator site on the silica surface was achieved by the treatment of the silica with γ-aminopropyltriethoxysilane. Polyamidoamine dendrimer was propagated from silica surface by repeating two processes: (1) Michael addition of methyl acrylate to surface amino groups, and (2) amidation of the resulting esters with ethylenediamine. The amino group content of the resulting silica increased from 0.40 mmol/g to 8.30 mmol/g after 10th generation. In addition, the percentage of grafting increased with 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’ highly 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 polymer onto silica surface were also investigated. Dendrimer-like highly branched polymer grafted ultrafine silicas gave a stable dispersion in a good solvent for the polyamidoamine dendrimer.