Preparation And Characterization Of Magnetic Polymer Microspheres

Magnetic polymer microspheres are kinds of microspheres with magnetism and special structure, which composed of polymer and inorganic magnetic materials. They not only can be endowed with functional groups on surface by copolymerization or surface modification, but also can be separated conveniently from mixtures under enforced magnetic field. Therefore they have gained broad applications in biomedicine, bioengineering, cytology and separating engineering. Because of their super- paramagnetic properties, they can be rapidly separated from solution under magnetic field. In the past decades, a great number of scientists have dedicated their efforts to preparation of different kinds of magnetic polymer microspheres and many strategies have been performed to producing magnetic polymer microspheres. Up to now, there are three ways to prepare magnetic polymer microspheres: (1) Encapsulation of magnetic particles with preformed natural or synthetic polymers is the simple and classical method to prepare magnetic polymer microspheres; (2) Another method is developed by Ugelstad through direct precipitation of iron salt inside the porous polystyrene particles; (3) The third method is to suspend magnetic particles in the dispersed phase and then polymerize the monomer in the presence of the magnetic particles to form magnetic polymer microspheres.In this article, magnetic polymer microspheres were prepared with monodispersity and strong magnetic responsivity on the base of others' research. Fe₃O₄ particles were used to be the core material of the microspheres, which were prepared by chemical co-precipitation method. The Monodisperse magnetic polystyrene microspheres of small Fe₃O₄ particles were prepared by improved emulsion polymerization using dispersion polymerization of styrene, SDBS as emulsifier, water/ alcohol mixture as reaction medium and KPS as initiator. The conditions of the polymerization were optimized by orthogonal test .The influence of polymerization temperature, initiator concentration, emulsifier dosage, ratio of alcohol / water and the stirring speed on particle size and particle size distribution was discussed, And the best reaction conditions were gotten. The studies showed that lower polymerization temperature, lower initiator concentration, higher emulsifier dosage and less ratio of alcohol/ water were advantaged to get magnetic PS microspheres with smaller particle size and higher uniformity.The superface topography, particle size and particle size distribution of the magnetic microspheres were observed with an optical microscopy and SEM. The magnetism can be carried out clearly using a magnet of magnetic field about 400GS and spectrophotometer. The structure was carried out with Furier transfer infrared. The degree of the thermal stability of the magnetic microspheres was carried out with a thermogravimetric analysis. The results indicated that the magnetic microspheres were superparamagnetic, excellent stability, dispersibility and acid-resistiviry, well shaped spheres and smooth surface.