| In recent years, magnetic polymeric particles, due to their relatively rapid and easy magnetic separation, have been used in biomedical and bioengineering such as cell separation, immunoassy and nucleic acids concentration. In addition, magnetic polymeric particles offer a high potential in several areas of application such as detoxification of biological fluid and the magnetic guidance of particle systems for specific drug delivery process.So far, although numerous synthetic routes, such as suspension polymerization, emulsion polymerization, dispersion polymerization, etc, have been developed to produce magnetic composite microspheres, there are still a lot of problems need to be resolved for preparing ideal and useful magnetic composite microspheres. These problems include low magnetic content, low efficiency of encapsulation, big size, polydispersity of particle size, the contamination of composite microspheres by some additives, etc.It is realized recently that the preparation of high quality magnetic composite microspheres relies on the breakthrough of synthesis approaches and the detail understanding of the polymerization mechanism in the presence of magnetic inorganic particles. The main objective of this dissertation is to develop novel methodologies to prepare magnetic composite microspheres, to find the relationship between the structure of composite microspheres and the preparation method, to elucidate mechanism of preparation.Improved emulsion polymerization, miniemulsion polymerization, living radical DPE method had been developed in this dissertation to prepare microspheres having different particle size. Some special surface treatment methods were adopted to improve the interface interaction between the polymer and magnetic particles in order to increase the encapsulation efficiency. The ultrasonic technique, some organic solvents and several functional steric stabilizers were applied to improve the quality of final magnetic particles.PS/iron oxides magnetic composite microspheres with the size 80-210nm were prepared via improved emulsion polymerization. Several key factors, ultrasonic dispersion, water/organic solvent mixing medium, surfactant, were used and adjusted in order to obtain composite particles with better monodispersity and less organicimpurities. The effect of these parameters on the variation of final particle size and size distribution, the morphology, magnetic content and magnetic response were investigated in detail. In terms of experiment dates, a new hypothesis has been developed to elucidate the mechanism of preparation of magnetic composite microsphere in the presence of ferrofluid via improved emulsion polymerization.Fundamental research on the miniemulsion polymerization to prepare magnetic composite particles was carried out. The work mainly focused on the effect of surface treatment method of magnetic nanoparticles on the final particle size, size distribution and some magnetic properties of the composite microspheres. The magnetic composite microspheres with better size distribution and structure, possessing higher conversion rate of polymer and ideal magnetic properties were synthesized by adding an amount of dispersant, Disperbyk-106, bearing much polar functional groups. By controlling parameters superparamagnetic magnetic composite microspheres with size less than 300nm, magnetic content 24% and saturation magnetization 47emu/g could be prepared by miniemulsion polymerization.A novel method with the addition of 1,1-diphenylethylene (DPE) was firstly developed in this dissertation to prepare clean magnetic composite microspheres, which was one kind of living radical polymerization. The results showed that appropriate copolymer composition and processing techniques were fairly important in the preparation of composite magnetic microspheres. Superparamagnetic magnetic composite microspheres with size less than 500nm, magnetic content 22% and saturation magnetization 32.5emu/g could be prepared by this novel method. It is proposed that the polymer...
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