Made available in DSpace on 2014-12-17T15:42:27Z (GMT). No. of bitstreams: 1 JulianaSN.pdf: 1926581 bytes, checksum: 39f0578ac55e6915852da779ae1734b5 (MD5) Previous issue date: 2007-10-18 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Magnetic particles are systems with potential use in drug delivery systems, ferrofluids, and effluent treatment. In many situations, such as in biomedical applications, it is necessary to cover magnetic particles with an organic material, as polymers. In this work, magnetic particles were obtained through covering magnetite particles with poly(methyl methacrylate‐comethacrylic acid) via miniemulsion polymerization process. The resultant materials were characterized X‐ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), zeta potential (��) measurements and vibrating sample magnetometry (VSM). XRD results showed magnetite as the predominant cristalline phase in all samples and that cristallites had nanometric dimensions. Thermogravimetric analysis revealed an increase in polymer thermal stability as a result of magnetite encapsulation. TGA results showed also that the encapsulation efficiency was directly related to nanoparticles s hidrofobicity degree. VSM measurements showed that magnetic polymeric particles were superparamagnetic, so that they may be potentially used for magnetic (bio)separation / Part?culas magn?ticas s?o sistemas com potencial de uso em libera??o controlada f?rmacos, ferrofluidos e tratamentos de efluentes. Em muitas situa??es, como em aplica??es biol?gicas, ? necess?rio revestir as part?culas magn?ticas com um material org?nico, como pol?meros. Neste trabalho, part?culas magn?ticas foram obtidas pelo revestimento de part?culas de magnetita por poli(metacrilato de metila‐co?cido metacr?lico) via processo de polimeriza??o em miniemuls?o. Os produtos obtidos foram caracterizados por difra??o de raios X (DRX), espectroscopia de absor??o no infravermelho por transformada de Fourier (FTIR), an?lise termogravim?trica (TG), medidas de potencial zeta (��) e magnetometria de amostra vibrante (MAV). Os resultados de DRX mostraram que a magnetita ? a fase cristalina dominante em todas as amostras, tendo seus cristalitos dimens?es nanom?tricas. A an?lise termogravim?trica revelou um aumento na estabilidade t?rmica das amostras com magnetita encapsulada e que a efici?ncia de encapsula??o foi diretamente relacionada ao grau de hidrofobiza??o das nanopart?culas. Medidas de magnetiza??o mostraram que as part?culas polim?ricas magn?ticas foram superparamagn?ticas, podendo ser satisfatoriamente utilizadas em processos de (bio)separa??o magn?tica