Magnetic hydrogels with supracolloidal structures prepared by suspension polymerization stabilized by Fe2O3 nanoparticles

Magnetic hydrogels with supracolloidal structures were fabricated by suspension polymerization of N-isopropylacrylamide (NIPAm) and/or acrylamide (Am) stabilized by Fe2O3 nanoparticles. Fe2O3 nanoparticles can self-assemble at liquid-liquid interfaces to form stable water in oil Pickering emulsion droplets. Monomers dissolved in suspended aqueous droplets were subsequently polymerized at 60 degrees C. When NIPAm was homopolymerized the PNIPAm produced deposited from the interior water phase onto the interface to form Fe2O3/PNIPAm nanocomposite shells because of its hydrophobicity at the reaction temperature. Magnetic and thermosensitive hollow microcapsules were obtained. When Am was homopolymerized magnetic core-shell microcapsules with PAm hydrogel cores and Fe2O3 nanoparticle shells were obtained. When NIPAm and Am were co-polymerized, magnetic hydrogel microcapsules with two kinds of supracolloidal structures were obtained varying with the NIPAm/Am ratio. These microcapsule beads may find applications as delivery vehicles for biomolecules, drugs, cosmetics, food supplements and living cells. Suspension polymerization based on Pickering emulsion droplets opens up a new route to synthesize a variety of hybrid hydrogels with supracolloidal structures. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.