Synthesis Of Magnetic Nanoparticles Monodispersing In Organic Solvent And Its Application To Prepare Magnetic Polymer Microspheres

Magnetic Polymer Microspheres (MPM) is a kind of novel functional materials which have both properties of magnetic materials and of polymer materials. MPM can be directly coupled with a lot of biological active materials like enzyme , cell , antibody , drugs and polymers because the shell is polymers which has abundance functional groups such as —OH , — COOH , — NH₂ and — CHO or is easy to be modified to meet various requirements;the core is magnetic materials which makes the MPM separated quickly and easily from mixtures by exterior magnetic field . Heretofore, MPM has exhibited extensive applications to biomedicine (for example, carrier of enzyme, separation of cells and antibody, target delivery of drug, contrast enhancement in magnetic resonance etc .) , bioengineer and materials . It has aroused extensive scientific and technological interest in lately 20 years.One of the main difficulties in synthesis core-shell magnetic polymers is the monodispersion of the magnetic nanoparticles in organic monomer. In this paper, on the basis of summarizing the research fruits of magnetic and magnetic polymer microspheres worldwide, a kind of oleic acid-coating magnetic nanoparticles which can disperse uniformly in various organic solutions was prepared with an improved sol-gel process. X-ray diffraction measurements indicate the nanoparticles were pure Fe₃O₄. The results of laser scattering measurements shows that the nanoparticles are highly monodisperse and the average size is 165nm(polydispersity 0.005). Vibrating sample magnetometer(VSM) indicates that the magnetic nanoparticles are superparamagnetic and the saturation magnetization is 44.8emu/g.The monodisperse magnetic fluid was applied to prepare MPM by improved microsuspension polymerization. The structure, particle size and magnetic properties of MPM were characterized and the reaction mechanism was analyzed. Such influencing factors as the indissoluble assistant and the stirring speed were investigated. The transmission electron microscopy indicates that the MPM is monodispers and the surface of MPM is smooth. The results of VSM show that the MPM exhibits superparamagnetism and the saturation magnetization is 8.1 emu/g. The magnetic content was 10.63% measured by DSC.In order to increase the number of such groups as —COOH, —OH on the surface of MPM, the MPM was modified by co- polymerization with crylic acid and its derivatives.