Synthesis and characterization of polymer nanocomposites containing magnetic nanoparticles

Magnetic poly (methyl methacrylate) nanocomposites were prepared using oleic acid coated cobalt ferrite and magnetite nanoparticles. Both nanofillers had a similar effect in shifting the glass transition temperature from that of the neat polymer. The cobalt ferrite nanocomposite had magnetic hysteresis at 2 and 300 K and the magnetite nanocomposite had magnetic hysteresis at 2 K and superparamagnetic behavior at 300 K. Surprisingly, zero field cooled magnetization measurements for the cobalt ferrite nanocomposite showed a peak at similar to 250 K, in contrast with measured hysteresis at 300 K. On the other hand, ac susceptibility measurements up to 400 K did not show any peaks for the cobalt ferrite nanocomposite. These measurements suggest the importance of ac susceptibility measurements in characterizing the magnetic properties of polymer nanocomposites. (C) 2010 American Institute of Physics. [doi:10.1063/1.3358017]