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/Fe3O4 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．