Toward Designer Magnetite/Polystyrene Colloidal Composite Microspheres with Controllable Nanostructures and Desirable Surface Functionalities

摘要

An effective method was developed for synthesizing magnetitepolymer colloidal composite microspheres with controllable variations in size andnshape of the nanostructures and desirable interfacial chemical functionalities, usingnsurfactant-free seeded emulsion polymerization with magnetite (Fe3O4) colloidalnnanocrystal clusters (CNCs) as the seed, styrene (St) as the monomer, andnpotassium persulfate (KPS) as the initiator. The sub-micrometer-sized citrate-acidstabilizednFe3O4 CNCs were first obtained via ethylene glycol (EG)-mediatednsolvothermal synthesis, followed by 3-(trimethoxysilyl)propyl methacrylate (MPS)nmodification to immobilize the active vinyl groups onto the surfaces, and then thenhydrophobic St monomers were polymerized at the interfaces to form the polymernshells by seeded emulsion radical polymerization. The morphology of thencomposite microspheres could be controlled from raspberry- and flower-likenshapes, to eccentric structures by simply adjusting the feeding weight ratio of thenseed to the monomer (Fe3O4/St) and varying the amount of cross-linker divinyl benzene (DVB). The morphological transitionnwas rationalized by considering the viscosity of monomer-swollen polymer matrix and interfacial tension between the seeds andnpolymer matrix. Functional groups, such as carboxyl, hydroxyl, and epoxy, can be facilely introduced onto the compositenmicrospheres through copolymerization of St with other functional monomers. The resultant microspheres displayed a highnsaturation magnetization (46 emu/g), well-defined core−shell nanostructures, and surface chemical functionalities, as well as ansustained colloidal stability, promising for further biomedical applications.