In situ Production of Polystyrene Magnetic Nanocomposites through a Batch Suspension Polymerization Process

This work presents the synthesis of micro-sized polystyrene magnetic beads by in situ incorporation of oleic acid-modified Fe3O4 magnetic nanoparticles via a suspension polymerization process. Fe3O4 nanoparticles with superparamagnetic characteristics were obtained through a coprecipitation technique. These particles present an average diameter equal to 7.4 +/- 4.6 nm, as determined by AFM. This result is in agreement with the crystallite size of single domains calculated by using Scherrer's equation, which was equal to 7.7 nm, based on XRD measurements. The obtained materials were also studied using TGA. The weight loss behavior was independent of the Fe3O4 content and the stability to the thermal degradation was also not improved by magnetic nanoparticles present in the composite. Polystyrene/Fe3O4 magnetic nanocomposites exhibited the same diffraction peaks observed in the pure Fe3O4, which indicates that nanoparticles inside the composites preserved the structure and properties of pure Fe3O4. It was also shown that nanosized polystyrene particles, dispersed in the aqueous phase, are obtained due to the stabilization effect of the oleic acid on the styrene droplets. A cross-section of polystyrene magnetic particles showed empty spherical regions, attributed to the encapsulation of water microdroplets during the polymerization reaction. The obtained polymeric materials also presented good magnetic behavior, indicating that the modified Fe3O4 nanoparticles were successfully dispersed in the polystyrene particles.