Controlled Room Temperature Synthesis of CoFe₂O₄ Nanoparticles through a Block Copolymer Nanoreactor Route

Abstract

The synthesis and characterization of well-dispersed, CoFe 2 O 4 nanoparticles within a polymer matrix at room temperature are reported. Comparable inorganic synthetic methods require heating at high temperatures in order to produce this particular mixed-metal oxide composition. Our modification of prior reported templating schemes using block copolymers consists of introducing a mixture of metal salts to a polymer solution before any microphase separation of the block copolymer constituents can occur, thus allowing fast diffusion of metals to the functional polymer backbone. The diblock copolymer matrix was synthesized using ring-opening metathesis polymerization of norbornene derivatives. The self-assembly of the mixed-metal oxide within the polymer template was achieved at room temperature by introducing a mixture of FeCl 3 and CoCl 2 into one of the functional polymer blocks and by subsequent processing of the copolymer by wet chemical methods to substitute the chlorine atoms with oxygen. CoFe 2 O 4 nanoparticles were thus formed within the spherical microphase-separated morphology of the diblock copolymer, which serves as the templating medium. Transmission electron microscopy, Fourier transform infrared spectroscopy, and wide-angle X-ray diffraction were used to characterize the nanocomposite morphology, oxide chemical composition, and process of oxide formation.