Controlled radical polymerization of styrene with magnetic iron oxides prepared through hydrothermal, bioinspired, and bacterial processes

Controlled/living radical polymerization was examined with the use of magnetic iron oxide (Fe₃O₄) prepared through various processes, including hydrothermal synthesis, a bioinspired process, and magnetotactic bacteria. Prior to the use of various types of Fe₃O₄, commercially available Fe₃O₄ was employed as a heterogeneous catalyst for styrene polymerization in conjunction with an alkyl halide as an initiator. Under appropriately optimized conditions, with the addition of Ph₃P in a solvent mixture of toluene and DMF, the polymerization proceeded in a well-controlled manner. In addition, solid Fe₃O₄ was recovered using a magnetic approach and was reused for a polymerization reaction. The effects of stirring on the polymerization rate suggest that the surface of Fe₃O₄ is responsible for the catalysis in polymerization. Fe₃O₄ samples prepared through various processes were then used for styrene polymerization and showed different activities depending on the preparation process. In particular, Fe₃O₄ prepared through hydrothermal synthesis exhibited a much higher activity compared with commercial Fe₃O₄.