Magnetic iron oxide nanoparticles were prepared by chemical coprecipitation of ferrous and ferric salts in the alkaline medium, and water-dispersed magnetic fluids were achieved by dispersing the nanoparticles into the aqua ammonia solution of oleic acid, then magnetic Fe₃O₄@P(St-GMA) microspheres were achieved by soap-free emulsion polymerization of styrene and glycidyl methacrylate in the presence of magnetic fluids. The effecting factors to the fractional conversion of polymerization such as styrene content, ferrofluid content, initiator content and temperature, were examined in detail. To confirm the iron oxide nanoparticles were encapsulated by P(St-GMA), one sample selected was characterized by TEM, TGA and VSM.

Key words: chemical coprecipitation, soap-free emulsion co-polymerization, conversion, magnetic fluids, magnetic microspheres