The Preparation And Properties Of P(St/MMA/AA)/Fe₃O₄ Magnetic Composite Microspheres By Controlled Radical Polymerization

Magnetic polymer microsphere is a kind of microsphere with magnetism and special structure, which is composed of polymer and inorganic magnetic materials. It can not only be endowed with functional groups on surface by copolymerization or surface modification, but also be separated quickly and easily from mixtures by exterior magnetic field. Therefore, since 1970's, as a new type of functional material it has gained broad applications in biomedicine, cytology, bioengineerings, separating engineerings and stealth technologies.On the basis of summarizing the research fruits of magnetic polymer microspheres worldwide, a novel method with the addition of 1,1-diphenylethlene (DPE) was firstly developed in this dissertation to prepare clean magnetic composite microspheres, which was one kind of living radical polymerization. The characteristic of this method was that no surfactant was used during the polymerization, and the short chain of the copolymer had the function of emulsification. The polymerization could be controlled with the use of DPE. The carboxyl of the copolymer's short chain could make it adsorb to the surface of the magnetic inorganic particle, and then the polymerization could be go on on the surface of the magnetic inorganic particle.The magnetic content of magnetic composite microspheres prepared by this method can reach 20%, and the size of the magnetic composite microspheres were about 300nm. There was no impurity on the surface of the magnetic composite microspheres because of no surfactant was added to the system during the course of preparing.In this article, some influencing factors, such as the added quantity of AA, DPE, magnetic inorganic particle, the PH of the system, were investigated emphatically. It was found that as the addition of the AA, the capability of themagnetic composite microspheres turned better, and then to worse, then better. The best amount of the DPE was 2%. The best addition time of the magnetic inorganic particle was 5~15 minute, and the best amount of the magnetic inorganic particle was 50%. The best PH was 5.On this condition, the mechanism of DPE was researched. The progress of the preparation included three steps : prepolymerization, the adsorption of the copolymer's short chain on the surface of the magnetic inorganic particle and the polymerization on the surface of the magnetic inorganic particles.The surface modification of magnetic inorganic particle was studied in this article. The surface hydroxyl of the magnetic inorganic particle must be propriety. If not ,the result will be worst.