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 °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.