The Preparation Of Core-shell Magnetic Ploymer Microspheres

Magnetic polymer microsphere is a kind of polymer material with special structure and magnetism, made by combining the polymer microspheres and the inorganic nano-particle magnetic material. The material has a wide application prospect in many areas, such as biomedicine (clinical enzyme targeted medicine), cytology (cell markers, cell separation, e.g.), bioengineering (immobilization of enzyme) and the load transportation of the catalyst, as its dual nature of the polymer microspheres and the magnetic microspheres and being a kind of new functional polymer. So many countries in the world have been widely attracted by the study and development of the magnetic nano-composites.On the base of concluding the achievements of the formers, the paper improves the experiment method, making the magnetic nano-composites, multilayer-centered and nuclear-shell structured, with the way of combining the electrostatic self-assembly and seeded emulsion polymerization.The polystyrene microspheres with negative charge on the surface was firstly made by the emulsifier-free emulsion polymerization. Then the particle Fe3O4 was modified to have positive charge by the surfactant CTAB and the water-based magnetic fluids were got by ultrasonic dispersion. This multilayer-centered and nuclear-shell structured magnetic nano-composites, with the PS microspheres as its kernel and the magnetic particle layer in the middle and the polymer layer covered in the outside, were obtained through the way of combining the electrostatic self-assembly and seeded emulsion polymerization. The particle is structure stable, magnetism strong, surface smooth, size tunable and strongly stable. With the method, low cost and adaptable, the thickness of the covered layers can be controlled through the nanometer scale and the particles with special surface groups could be made to meet different application requirements.Through a series of experimental analysis, it is discovered that the three layered (PS/Fe3O4/PMMA) and core-shell structured composite microspheres, good ball shaped ( diameter: about 1000 nm), disperse equally in the water without agglomeration, with a proportion of about 40wt% magnetic particle. The trait of the Magnetic polymer microspheres is improved to a large degree with superparamagnetic particles as the raw material. The superparamagnetic polymer microspheres, with a diameter of about 890nm, contain a proportion of magnetic particle about 50wt%.