Synthesis And Magnetic Properties Of Block Copolymer-CoFe2O4 Nanoclusters
- PDF / 641,353 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 110 Downloads / 296 Views
Synthesis And Magnetic Properties Of Block Copolymer−CoFe2O4 Nanoclusters Sufi R. Ahmed, and Peter Kofinas Department of Materials & Nuclear Engineering, University of Maryland,College Park, MD 20742−2115, USA. ABSTRACT 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 oK and 5 oK. 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. INTRODUCTION Metal nanoclusters are subject of current interest because of their unusual optical, electronic and magnetic properties, which often differ from their bulk properties. Recently metal nanoclusters of Cu, Ag, Pd, Pt[1,2,3] and metal oxide nanoclusters of Fe2O2[4] and CuO have been synthesized within microphase separated domains of diblock copolymers. The self−assembled nature of the microdomains allows very good control over the shape and size of the nanoclusters. The interfaces between the blocks of the diblock copolymers play an important role in the nucleation and growth of clusters, and induce a narrow size distribution. The polymer matrix also provides kinetic hindrance to aggregation of nanoclusters. Cobalt ferrite, CoFe2O4 is a well known hard magnetic material with very high cubic magnetocrystalline anisotropy, high coercivity and moderate saturation magnetization. In this paper we describe the synthesis and the magnetic properties of polymer based − CoFe2O4 nanocomposites. This is the first report on the room temperature synthesis of mixed metal oxide nanoclusters dispersed within a polymer matrix.
KK10.10.1
EXPERIMENTAL Polymer synthesis and mixed metal oxide formation: Diblock copolymers were synthesized by ring opening metathesis polymerization (ROMP) of norbornen
Data Loading...
