Synthesis and applications of water-dispersible microspheres containing arborescent PAMAM surfaces

This manuscript reports on a novel synthetic approach to engineer water-dispersible microspheres with short poly(amidoamine) (PAMAM) chain grafted on their surface. These core-shell polymeric microspheres have a large amount of amine groups on their surface obtained via starburst reactions. First, monodispersed poly (methyl methacrylate)-co-poly(glycidyl methacrylate) (P(MMA/GMA)) microspheres were prepared by surfactant-free emulsion polymerization. Afterwards, Michael reaction and subsequent amidation reactions were carried out repetitively to synthesize arborescent PAMAM chains grafted on the surface of the P(MMA/GMA) microspheres. The resulting PAMAM-grafted microspheres exhibit good dispersibility in aqueous environments. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) demonstrate the successful grafting; furthermore, the crosslink degree of the P(MMA/GMA) microspheres as well as the PAMAM chain length affect the stability of the resulting core-shell microspheres, as experimentally tested by heat treatment and acidic treatment. Easily, the PAMAM chains are protonated at low pH, and are thus able to effectively adsorb negatively-charged magnetic nanoparticles. Bright photoluminescent (PL) water-dispersible polymeric microspheres are fabricated readily via the reaction of the surface amine groups and traditional fluorescent molecules, namely fluorescein isothiocyanate (FITC). (C) 2008 Wiley Periodicals, Inc.