Magnetic properties of CoFe2O4 nanoparticles synthesized through a block copolymer nanoreactor route

The development of self-assembled magnetic ${\mathrm{CoFe}}_2{\mathrm{O}}_4$ nanoparticles within polymer matrices at room temperature is reported. Diblock copolymers consisting of poly (norbornene) and poly (norbornene-dicarboxcylic acid) (NOR/NORCOOH) 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 ${}^{\mathrm{57}}\mathrm{Fe}$ Mössbauer spectroscopy. The ${\mathrm{CoFe}}_2{\mathrm{O}}_4$ nanoparticles are uniformly dispersed within the polymer matrix, and have an average radius of $\text{4.8±1.4\hspace{0.17em}}\mathrm{nm}.$ The nanocomposite films are superparamagnetic at room temperature and ferrimagnetic at 5 K.