The development of self-assembled magnetic CoFe 2 O 4 nanoparticles within polymer matrices at room temperature is reported. Diblock copolymers consisting of poly ͑norbornene͒ and poly ͑norbornene-dicarboxcylic acid͒ ͑NOR/NORCOOH͒ were synthesized. The self-assembly of the mixed metal oxide within the NORCOOH block was achieved at room temperature by processing the copolymer nanocomposite using wet chemical methods. Morphology and magnetic properties were determined by superconducting quantum interference device magnetometry, transmission electron microscopy, wide angle x-ray diffraction, and 57 Fe Mössbauer spectroscopy. The CoFe 2 O 4 nanoparticles are uniformly dispersed within the polymer matrix, and have an average radius of 4.8Ϯ1.4 nm. The nanocomposite films are superparamagnetic at room temperature and ferrimagnetic at 5 K.

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We synthesized the block copolymer of poly(norbornene-dicarboxcylic acid) and poly(norbornene) at room temperature, using ring opening metathesis polymerization. We then templated the CoFe 2 O 4 nanoparticles within the polymer matrix, utilizing the self-assembled nature of the block copolymer. We used transmission electron microscopy, superconducting quantum interference device magnetometry, and X-ray powder diffraction to investigate the morphology and magnetic properties of the nanocomposites. The nanocomposite films are ferrimagnetic at room temperature. The CoFe 2 O 4 nanoparticles are spherical and have an average radius of 8 7 0 4 nm. The nanoparticles are uniformly distributed within the polymer matrix with a nanoparticle density of 110 9 particles/cm 2 .

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The overall goal of this research is to explore techniques for the development of novel binary magnetic oxide nanoclusters uniformly distributed within a polymer matrix. These CoFe2O4 nanoclusters were synthesized at room temperature, and are confined within the self-assembled nanoscale structure exhibited by block copolymers templates. The diblock copolymers were synthesized by ring opening metathesis polymerization of norbornene and norbornene trimethylsilane and the binary magnetic oxide was introduced through a nanoreaction scheme using wet chemical methods. Transmission electron micrographs of microtomed thin sections of these nanocomposites show that the metal oxide nanoclusters are ellipsoidal in shape and are uniformly distributed within the polymer matrix. A SQUID magnetometer was used to study the magnetic properties of the polymeric nanocomposites at applied fields up to 5 Tesla and at a temperature range between 300 °K and 5 °K. Mössbauer spectroscopy was used to study the structure of the nanoconfined metal oxide, and confirmed the synthesis of CoFe2O4 nanoclusters exhibiting an inverse spinel structure. This study provided a better understanding of the nucleation, growth and distribution of metal oxide nanoclusters within block copolymers and indicated ways to control the magnetic properties of polymeric based nanocomposite materials. The development of such binary metal oxide - block copolymer nanocomposites is targeting the functionalization of such nanostructures into magnetic device technologies.