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New solid and hollow monodispersed micron-sized organic-inorganic hybrid magnetic nan';lparticles have been recently prepared and characterized in our laboratory. The solid particles were formed by seeded polymerization of iron salts onto polystyrene monodispersed micron-sized (1-6 J.lID) particles. A further coating of these ferrite-coated particles with silica nanoparticles of significantly lower diameter (30-40 nm) was prepared by seeded polymerization of these particles with Si(OEt)4. The effect of the polystyrene surface composition on the ~ting of the polystyrene with ferrite and with silica is demonstrated. Hollow ferrite silica micron-sized particles were formed by burning off the polystyrene core of the former hybrid particles. Surface modification of these particles was performed by reacting these silica-coated particles with a variety of m-alcoholic reagents or m-alkylsilane compoWlds. The potential biomedical use of these ferrite-coated particles is also demonstrated and discussed.

Polyacrylonitrile/polystyrene micrometer‐sized composite particles of narrow size distribution were prepared by a single‐step swelling of uniform polystyrene template microspheres with emulsion droplets of methylene chloride containing the monomer acrylonitrile and the initiator benzoyl peroxide. Methylene chloride was then evaporated carefully, followed by polymerization of acrylonitrile at 70 °C within the shrunken template particles. Polymerization of acrylonitrile also occurred at the particles' surface due to the interaction of surface polyacrylonitrile oligoradicals with acrylonitrile dissolved in the aqueous phase. Uniform polyacrylonitrile particles of higher surface area were formed by dissolving the template polystyrene polymer of the composite particles. Surface and bulk characterization of the particles were performed by methods such as FTIR, elemental analysis, TGA‐DSC, XRD, XPS, advancing contact angle, light microscope, SEM and cross‐sectional TEM. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4847–4861, 2004

Poly(acrylonitrile)-poly(styrene) micrometer-sized composite particles with a narrow size distribution are prepared by single-step swelling of poly(styrene) uniform template microspheres in emulsion droplets of methylene chloride containing an acrylonitrile monomer and a benzoyl peroxide initiator. Methylene chloride is carefully evaporated with subsequent polymerization of acrylonitrile at a temperature of 70 ° C inside the shrunken template particles. Acrylonitrile is also polymerized at the particle surface due to the interaction of surface poly(acrylonitrile) oligoradicals with acrylonitrile dissolved in the aqueous phase. Uniform poly(acrylonitrile) particles with a larger surface area are formed by dissolving template poly(styrene) of the composite particles. The surface and bulk properties of the particles are investigated using Fourier transform IR (FTIR) spectroscopy, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction, X-ray photoelectron spectroscopy (XPS), contact-angle measurements, optical microscopy, scanning electron microscopy (SEM), and cross-sectional transmission electron microscopy (TEM).