Study On Preparation Of Magnetic Polymer Microspheres

Magnetic polymer microspheres composed of magnetic nanoparticles and polymer have been attracting much attention for their special character. Magnetic polymer microspheres can be easily prepared and be further processed to introduce various functional groups (such as–NH2,-OH,-CHO,-COOH) onto its surface area, further, enzyme, protein, cell and antibody, et al. can be coupled with, in addition, it will quickly move or separate in external magnetic field, so, magnetic polymer microspheres show promise of practical applications to the fields of cell separation, cell tagging, biologic analysis, enzyme immobilization, clinical diagnosis target medicine,DNA hybridization. Moreover, removal of polymer materials by physical and chemical methods from magnetic polymer microspheres to produce hollow materials, it also plays prominent roles in catalyst, magnetic record materials, magnetic resonance image, pigment and many other areas,In this paper, magnetic polymer microsphere preparation is illustrated, including magnetic powders preparation by precipitation, polymeric microspheres preparation by suspension polymerization and microemulsion polymerization , the spherical aggregates with a high magnetic content and magnetic polymeric microspheres preparation by self-assembly method. The samples were characterized by XRD,TEM, SEM, FTIR ,and VSM.In the first chapter, the current survey on the preparation, composing, applications of magnetic polymer microspheres were introduced. The correlative scientific problems needed to be solved were brought forward.In the second chapter, magnetic powders were synthesized by the coprecipitation method. The samples were characterized by XRD,TEM, and VSM. The results indicate that the as-synthesized magnetic powders are single-phase Fe₃O₄ with an average size of 10nm. Magnetic property measurement shows that at room temperature, the saturated magnetization of the magnetic powders is 69 A.m2.kg-1 when applied field is at 6kOe. In the third chapter, PSt microspheres were prepared by the suspension polymerization, and characterized by SEM. The result indicates that diameter of the as-prepared PSt microspheres is 10μm～15μm。In the fourth chapter, P(St-co-AA)microspheres were prepared by the microemulsion polymerization, and characterized by SEM,IR, The results indicate that the as-prepared P(St-co-AA)microspheres with carboxyl are spherical , the diameter is ca.70nm.In the fifth chapter, Fe₃O₄ nanoparticles were synthesized by the partial reduction method. Uniform P(St-co-AA) microspheres were prepared by microemulsion polymerization. The composite microsphere aggregates were prepared by electrostatic self-assembly and hydrogen bonding self-assembly. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), FTIR spectroscopy, the content of magnetic powders in the composite microsphere aggregates was determined by acid dissolution method. The result indicates that the as-prepared composite microsphere aggregates are uniform, spherical and porous. The content of magnetic powders in aggregates is 30.81%. The effects of pH, stirring on the preparation of aggregates have been investigated.In the sixth chapter, Uniform P(St-co-AA) microspheres were prepared by microemulsion polymerization. The Fe₃O₄/P(St-co-AA) microspheres with a high magnetic content were prepared by electrostatic self-assembly using P(St-co-AA) microspheres with Fe₃O₄ nanoparticles synthesized by co-precipitation. All samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and FTIR spectroscopy. The results indicate that the average sizes of polymer microspheres with carboxyl and the magnetic powders with single-phase Fe₃O₄ are ca.70 nm and 10nm, respectively. The obtained Fe₃O₄/ P(St-co-AA) with an average size of 800 nm is spherical and the content of magnetic powders in Fe₃O₄/ P(St-co-AA) is 15.8%. The preparation of Fe₃O₄/ P(St-co-AA) are strongly affected by pH, siring .In the last chapter, the author summarized the whole dissertation and bought forward some suggestions for future research work of preparation of magnetic microsphere.