The Preparation And Characterization Of Magnetic Polymer Microspheres With Functional Groups

The magnetic responsivity and the reactivity of the surface functional groups are main properties of magnetic composite polymer microsphere. At present, it is difficult to prepare this kind of microsphere with high stability between polymer and inorganic magnetic materials, large amount of enwrapped magnetic particles, large number of surface functional groups. As a result, the applications of magnetic polymer microsphere are often restrained.For the above problems, the preparation and characterization of magnetic composite polymer microsphere with carboxyl groups and amido groups are studied in this thesis. The properties of inorganic magnetic particles affect the magnetism of magnetic composite polymer microsphere. Fe3O4 was chosen in this article. There are two methods for preparing Fe3O4. One is the inverse emulsion method in which the effect of volume ratio of liquid paraffin with water, stirring rate, emulsifier's amount, emulsification time and amount of NaOH on magnetization, structure, diameter and distribution of microparticles was studied. Another is coprecipitation method in ammonia. The two methods were compared and the better result was chosen for preparing magnetic composite polymer microsphere. Acrylamide, crylic acid and N,N′-methylene bisacrylamide were chosen for preparing magnetic composite polymer microsphere with carboxyl groups in inverse emulsion. Acrylamide is monomer, crylic acid provide functional groups, and N,N′--methylene bisacrylamide is the cross-linking agent.Four factors were taken into account: the amount of acrylamide-crylic acid and N,N′-methylene bisacrylamide, reaction time, medium and the amount of Fe3O4. Effects of different conditions on shape, magnetic responsivity, the amount of the surface functional groups were studied. Through the orthogonal-designing experiments, the better project were obtained for preparing magnetic composite polymer microsphere with large amount of Fe3O4 and the surface functional groups. In this project, acrylamide is 10g, crylic acid is 1.3g, N,N′-methylene bisacrylamide is 0.1g, the total amount of Fe3O4 is 4g, reaction time is 120min. The effects of single factor on the properties of the magnetic microshphere were also discussed and the optimum preparation conditions were obtained for preparing magnetic composite polymer microsphere with 1.0 mmol/g carboxyl groups and 85% enwrapping efficiency. Styrene, divinylbenzene and N,N′-bis(3-aminopropyl)but-2-endiamide were chosen for preparing magnetic composite polymer microsphere with amido groups during soap-free emulsion polymerization. Styrene is monomer, N,N′-bis(3-aminopropyl)but-2-endiamide provide functional groups, and divinylbenzene is the cross-linking agent. Two factors were taken into account: the amount of Styrene -divinylbenzene -N,N′-bis(3-aminopropyl)but-2-endiamide and reaction time. Effects of different conditions on shape, magnetic responsivity, the amount of the surface functional groups were studied. Through changing the structure of functional monomer, the reactivity of functional groups could be improved. The amine which couldn't polymerize were introduced on the magnetic microsphere surface and the stability of magnetic composite polymer microsphere were also improved. The magnetic composite polymer microsphere with 0.24 mmol/g amido groups and 22% enwrapping efficiency were prepared.