Physical and chemical properties of magnetite and magnetite-polymer nanoparticles and their colloidal dispersions

The properties of polymer-coated magnetite nanoparticles, which have the po tential to be used as effective magnetic resonance contrast agents, have be en studied. The magnetite particles were synthesized by using continuous sy nthesis in an aqueous solution. The polymer-coated magnetite nanoparticles were synthesized by seed precipitation polymerization of methacrylic acid a nd hydroxyethyl methacrylate in the presence of the magnetite nanoparticles . The particle size was measured by laser light scattering. It was shown th at the particle size, variance, magnetic properties, and stability of aqueo us magnetite colloidal dispersion strictly depend on the nature of the stab ilizing agent. The average hydrodynamic radius of the magnetite particles w as found to be 5.7 nm in the stable aqueous colloidal dispersion, An inclus ion of the magnetite particle into a hydrophilic polymeric shell increases the stability of the dispersion and decreases the influence of the stabiliz ing agent on the magnetic and structural properties of the magnetite partic les as was shown by X-ray diffraction and Mossbauer and IR spectroscopy, as well as by vibrating sample magnetometry. The variation in the polymeric s hell size and the polymer net density can be useful tools for evaluation of the polymer-coated magnetite particles as effective contrast agents. (C) 1 999 Academic Press.