Research Of The Preparation Technology For Oil-based Ferrofluid And Preparation Of Magnetic Polymer Microspheres With Functional Group

Nano-magnetic materials originated in late 1970s. Now it became one of the most promising new magnetic materials. Compared with the traditional magnetic materials, nano-magnetic materials manifest many outstanding qualities, such as superparamagnetism and higher coercivity. Fe₃O₄ is an important spinel type ferrite, one of the widely-used soft magnetic materials. Because of its magnetic sensitivity and gas and humidity sensitivity, Fe₃O₄ nanoparticles display extensive application prospect in such fields as high density record materials, magnetic fluids materials, magnetic polymer microspheres, gas and humidity sensors, magnetic resonance imaging and drug controlled releasing. At present, the research about magnetic fluids and polymer microspheres is popular.However, how to get the oil-based magnetic fluids with good dispersibility and stability is a critical problem.In this paper, oleic acid-coated Fe₃O₄ magnetic fluids, which can be dispersed in different organic media, were successfully synthesized by studying six different preparing methods. The results of infrared spectrum and X-rays spectrum show the surface of Fe₃O₄ particles was coated by oleic acid. The crystal shape of Fe₃O₄ was not affected by the adding of surfactants or organic solvents during the preparation of oil-based magnetic fluids. The magnetic content was the highest(12%) when fresh Fe₃O₄ particles were directly dispersed into the organic solvents without dryness after washing. Moreover, this kind of Fe₃O₄ nanoparticles has narrow diameter distribution, most in the range of 6-10nm. When the organic solvent was added during the preparation of Fe₃O₄, the fluids had more narrow diameter distribution, most in the range of 5-7nm. The magnetic content is about 10% and this kind of fluids had good magnetic response and high stability.The research focus of polymer magnetic microspheres is how to acquire monodispersing polymer magnetic microspheres with high magnetic contens and abundant functional groups on the surface. Epoxy groups can be transformed into many "active" groups. In this paper, magnetic microspheres are obtained by dispersion polymerization of styrene and glycidyl methacrylate in the present of oil-based or water-based magnetic fluids. The average size of microspheres is smaller than 3μm and the microspheres are almost monodispersed. The magnetic content is 2.5%. The surface of microspheres is smooth and Epoxy groups content is about 0.02 mmol/g. The monomer conversion is larger than 75%. The effects of dispersing medium, stabilizing agents, water/oil-based magnetic fluids on the mircrospheres sizes and magnetic content are also studied.