Preparation of magnetic composite microspheres by miniemulsion polymerization and their characterization

Submicron polystyrene/magnetite (PS/Fe₃O₄) composite microspheres were prepared by miniemulsion polymerization by using three kinds of low molecular weight polymer, Disperbyk-106, Disperbyk-108 and Disperbyk-111, as dispersant for magnetite particles and styrene. The effects of dispersants on the miniemulsion polymerization were discussed in detail, which showed that the addition of dispersant had a crucial effect on the preparation of the composite microspheres. Disperbyk-106, which contains both acid and basic groups, has a better effect on the improvement of the interface between magnetite particles and styrene. X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM) were conducted to character the magnetite particles and PS/Fe₃O ₄ composite microspheres. The average size of the composite microspheres is 340 nm and the magnetite content of the composite microspheres is around 8%. The XRD patterns showed that the magnetite particles preserve their crystal structure during the miniemulsion polymerization. The TEM observation revealed that magnetite particles distributed unevenly in the composite microspheres and there were some defects on the microspheres where magnetite particles agglomerated.