Microwave-assisted rapid synthesis of Fe3O4/poly(styrene-divinylbenzene-acrylic acid) polymeric magnetic composites and investigation of their structural and magnetic properties

We report a facile method for rapid synthesis of highly crystalline superparamagnetic Fe3O4 nanoparticles with crystallite size in the range of 25-33 nm via microwave synthesizer. The Fe3O4 stabilized with PVP was used to synthesize strong magnetized spherical polymeric magnetic composites (PMCs) in the range 0.3-1.5 mu m via microwave irradiated emulsion polymerization using vinyl monomers. The influence of reaction time and the amount of reactive reagents on the structure, morphology, thermal stability and magnetic property of synthesized PMCs were examined. HR-TEM revealed the incorporation of superparamagnetic Fe3O4 nanoparticles in the cross-linked polymeric matrix of poly(styrene-divinylbenzene-acrylic acid). The synthesized Fe3O4 nano particles exhibit superparamagnetic behavior at 300 K with a high saturation magnetization 67.5 emu/g for MNP-3. Interestingly, the as-synthesized magnetically responsive PMCs [Fe3O4/P(St-DVB-AA)] exhibit ferromagnetic properties with enhanced saturation magnetization in the measured temperature interval of 10-350 K, which is in contrast with the superparamagnetic behavior of synthesized Fe3O4 nanoparticles. An excellent saturation magnetization 22.5 emu/g was noted for the composite PMC-10 loaded with similar to 24% magnetic nanoparticles. Further, the as-synthesized Fe3O4 nanoparticles and polymer magnetic composites exhibit the charge ordering (Verwey transition) at low temperature in the range 30-41 K and 23-25 K, respectively.