Synthesis of magnetic particle/organic hybrid from metalorganic compounds
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Synthesis of magnetic particle/organic hybrid from metalorganic compounds Toshinobu Yogo, Tomoyuki Nakamura, Wataru Sakamoto, and Shin-ichi Hirano Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan (Received 5 May 1998; accepted 18 March 1999)
A nanocrystalline magnetic particle/oligomer hybrid was successfully synthesized by polymerization of iron(III) 3-allylacetylacetonate (IAA) followed by in situ hydrolysis. An iron oxide particle/oligomer hybrid was synthesized by hydrolysis of the IAA oligomer under alkaline and reducing conditions by the addition of hydrazine or methylhydrazine. Crystalline particles of approximately 10 nm were found to be dispersed in the oligomeric matrix. The nanocrystalline particles were identified to be iron oxide spinel by x-ray diffraction analysis and electron diffraction. The nanometer-sized ferrimagnetic iron oxide particle/oligomer hybrid showed a typical superparamagnetic behavior.
I. INTRODUCTION
Inorganic/organic hybrid materials, such as Ormocer, Ormosil, and Ceramer,1–3 deserve great attention as newly emerging composite materials. The organic and inorganic phases constitute the nanostructure of the hybrid through chemical bonding. Various hybrid materials, including SiO2, TiO2, and ZrO2-based systems,4,5 have been synthesized from metalorganic compounds by hydrolysis and polymerization. Nanocrystalline magnetic particles show unique phenomena of superparamagnetism6 and quantum size effect.7 The magnetic properties of the fine particles depend on the crystalline phases, crystallinity, and particle sizes. Magnetic particle/organic hybrid has various potential applications in magnetic and medical uses, such as magnetic recording,8 magnetic fluid,6 magnetic ink, magnetic resonance imaging,9 and hyperthermia.10 Magnetic particle/organic composites have been synthesized by various methods, such as mixing of magnetic particles and organic phases, ion-exchange gels from ferrofluid materials,11 and particle formation in a polymer matrix.12 The blending of magnetic particles into polymers has the inevitable problem of particle agglomeration during processing. The generation of such particles in situ by hydrolysis of Fe(II) and Fe(III) ions in a polymer matrix is one of the most advantageous methods. ␥–Fe2O3 particles were reported to be formed from iron (II) salt in the polystyrene sulfonate polymer,13 polypyrrole sulfonate,14 and multibilayer agarose film.15 Metallic salts of iron, such as iron chloride and sulfonate, are readily converted to iron oxide in aqueous alkaline solutions at room temperature. However, simple iron salts are usually insoluble in organic solvents. The J. Mater. Res., Vol. 14, No. 7, Jul 1999
nucleation and growth of iron oxide proceed at the heterogeneous interface between polymer and aqueous phase because the polymer matrix is insoluble in aqueous solution. To control the homogeneous nucleation and growth of iron oxide particles in
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