Facile synthesis of monodisperse superparamagnetic Fe_3O _4/PMMA composite nanospheres with high magnetization

摘要

Monodisperse superparamagnetic Fe_3O_4/polymethyl methacrylate (PMMA) composite nanospheres with high saturation magnetization were successfully prepared by a facile novel miniemulsion polymerization method. The ferrofluid, MMA monomer and surfactants were co-sonicated and emulsified to form stable miniemulsion for polymerization. The samples were characterized by DLS, TEM, FTIR, XRD, TGA and VSM. The diameter of the Fe_3O _4/PMMA composite nanospheres by DLS was close to 90nm with corresponding polydispersity index (PDI) as small as 0.099, which indicated that the nanospheres have excellent homogeneity in aqueous medium. The TEM results implied that the Fe_3O_4/PMMA composite nanospheres had a perfect core-shell structure with about 3nm thin PMMA shells, and the core was composed of many homogeneous and closely packed Fe_3O_4 nanoparticles. VSM and TGA showed that the Fe_3O_4/PMMA composite nanospheres with at least 65% high magnetite content were superparamagnetic, and the saturation magnetization was as high as around 39 emug- 1 (total mass), which was only decreased by 17% compared with the initial bare Fe_3O_4 nanoparticles.