Superparamagnetni nanokompoziti na osnovi nanodelcev superparamagnetnega železovega oksida in polimetil metakrilata : doktorska disertacija

slovenian

doktorska dela

2010

Univerza v Mariboru, Fakulteta za kemijo in kemijsko tehnologijo

Presented work describes synthesis of superparamagnetic nanocomposites, based on superparamagnetic y-Fe2O3 nanoparticles and PMMA. Nanoparticles were synthesized by the coprecipitation of Fe2*/Fe3* ions from an aqueous solution. Oleic or ricinoleic acid coated nanoparticles were synthesized by the coprecipitation of Fe2*/Fe3* ions from an aqueous solution in the presence of oleic or ricinoleic acid. Preliminary study clearly demonstrated that it is impossible to prepare superparamagnetic nanocomposite of the y-Fe2Ot in the PMMA matrix without nanoparticles functionalization. Sample prepared by the mixing of the y-Fe2O3 and the PMMA in the acetone and subsequent precipitation of the polymer by water addition, was composed of two separated phases, as observed by transmission electron microscopy (TEM). The phases were identified as agglomerates of the y-Fe2O3 which were not encapsulated by the PMMA matrix. Nanocomposites were prepared by the precipitation polymerization of the methyl methacrylate in the presence of oleic acid coated nanoparticles. Methyl methacrylate was added to the colloidal suspension of the oleic acid coated nanoparticles in n-decane and in-situ polymerization was carried out at elevated temperatures. The content of nanoparticles was controlled by varying the nanoparticles/monomer ratio. The TEM analysis showed that the nanoparticles were well dispersed in the polymer matrix. The mechanism of formation of the polymer grain changes from homogeneous to heterogeneous nucleation as the ratio is increased. Nanocomposites retained their superparamagnetic nature even when encapsulated by polymer with concentrations up to 48 wt. Yo. The high loading of magnetic nanoparticles resulted in relatively high saturation magnetizations of the nanocomposites, up to 31 emu/g. Nanocomposite particles were prepared using the mini-emulsion polymeization of a monomer in the presence of the nanoparticles. A colloidal suspension composed of ricinoleic acid coated iron-oxide nanoparticles, the initiator and the ultrahydrophobe in the monomer, methyl methacrylate, was added to an aqueous solution of surfactant and then ultrasonified to promote the formation of the mini-emulsion. The polymenzation was initiated by raising the temperature. By changing the content of surfactant, nanocomposite particles with an average diameter ranging from -25 to -50 nm were obtained. Because of the high (-potential, the nanocomposite particles formed a stable suspension in water. TEM showed that the core of the prepared nanocomposite particles was composed of iron-oxide nanoparticles homogeneously distributed within a polymer matrix anda thin polymer shell. The content of magnetic nanoparticles dispersed in the polymer was as high as 39 wt. %, resulting in a high saturation magnetization of 27 emu/g.

07.08.2023