Block Copolymer-Mediated Formation of Superparamagnetic Nanocomposites

Well-defined diblock copolymers of bicyclo[2.2.1]hept-5-ene-2-carboxylic acid oxiranylmethyl ester, having both anchoring and steric stabilizing blocks in a 1:1 ratio, have been prepared by ring-opening metathesis polymerization (ROMP). The epoxy-containing block copolymer stabilized in situ generated iron oxide (gamma-Fe2O3) nanoparticles. The epoxy ester group provided strong chelation between the iron-oxide nanoparticle and the polymeric siderophores, producing a stable magnetic nanocomposite. The polymers were characterized by H-1 NMR, GPC, TGA, and DSC. The morphology and crystalline structure of the maghemite-block copolymer nanocomposites were evaluated with TEM and XRD, revealing highly crystalline, monodisperse gamma-Fe2O3 nanoparticles with an average size of 3-5 mm. Interactions between the maghemite nanoparticles and the polymer were observed by FTIR. SQUID magnetometric analysis of the nanocomposites demonstrated superparamagnetism at room temperature with high saturation magnetization.