Characterization of magnetic poly(methyl methacrylate) microspheres prepared by the modified suspension polymerization

The study focuses on the characterization of the superparamagnetic microspheres of poly(methyl methacrylate) (PMMA) prepared by the modified suspension polymerization. The nano-sized oleic acid-coated magnetite particles (OMP) mixed with methyl methacrylate (MMA) monomers and divinylbenzene were employed to produce the nonporous superparamagnetic PMMA microspheres. The morphology, composition and magnetic properties of the magnetic PMMA microspheres were characterized with the scanning electron microscopy, particle size analyzer, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, and superconductor quantum interference device. As a result, the obtained PMMA microspheres had the average particle size of 1.8-6.8 mu m and magnetite content of 4.74-10.85 wt%. The corresponding saturation magnetization of the PMMA microspheres was in the range of 2.04-851 emu/g. The diameter of the PMMA microspheres showing the polydispersity significantly decreased with the higher weight ratio of OMP to MMA. On the contrary, the magnetite content and saturation magnetization of the PMMA microspheres would increase with the higher weight ratio of OMP to MMA. Furthermore, the distinct relationships between the characteristics of magnetic PMMA microspheres and the weight ratio of OMP to MMA have been proposed. The magnetic PMMA microspheres show the good stability in the solution with the pH region of 2.1-12.9. (C) 2008 Wiley Periodicals, Inc.