Superparamagnetic Composite Colloids with Anisotropic Structures

We report a unified set of emulsion polymerization processes for the synthesis of a series of spherical and nonspherical magnetite−polystyrene (Fe 3 O 4 −PS) composite colloids with the superparamagnetic cores concentrically or eccentrically positioned inside polystyrene shells. The interfacial tension between the inorganic core and monomer-swollen polymer shell and the effect of swelling and phase separation have been employed to tune the morphology and structure of the composite colloids. The uniform size, anisotropic structure/shape, and the additional magnetic control make these colloidal particles ideal building blocks for the fabrication of novel functional devices and materials.