Synthesis of magnetic Fe3O4/polyamine hybrid microsphere using O/W/O Pickering emulsion droplet as the polymerization micro-reactorElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ra00997a

In order to obtain a magnetic polyamine microsphere, a magnetic oil-water-in-oil multiple emulsion droplet was used as the micro-reactor and template for polymerization. The influences of magnetite (NanoFe 3 O 4 ) and the polymer precursor polyethyleneimine (PEI) on the properties of an emulsion were investigated. After using hydrophobic CaCO 3 nanoparticles (SM-CaCO 3 ) in the emulsification, the liquid paraffin-in-water emulsion stabilized by NanoFe 3 O 4 and PEI was changed to an O/W/O Pickering emulsion. The investigation found that suspensions of 2 wt% SM-CaCO 3 in liquid paraffin should be emulsified with 1 wt% NanoFe 3 O 4 in 20 wt% PEI solution at a w of 0.5 in order to incorporate as much PEI as possible, in emulsion droplets, while avoiding the phase inversion of emulsion. After the crosslinking of PEI in the emulsion droplets by glutaraldehyde, a magnetic Fe 3 O 4 /polyamine microsphere with both hydrophilic and hydrophobic characteristics was obtained. The microsphere demonstrated an isoelectric point of 9.6. The magnetic capacity of NanoFe 3 O 4 decreased as a result of being trapped in the polyamine matrix of the microsphere. An O/W/O emulsion containing Fe 3 O 4 NPs and PEI was obtained using SM-CaCO 3 NPs as the stabilizer. In a droplet-to-droplet reaction mode, a magnetic polyamine microsphere was achieved by crosslinking PEI in the emulsion droplet with glutaraldehyde.