Syndiotactic polypropylenes and their copolymers with 1‐olefins were synthesized using two metallocene/MAO catalytic systems, and the effect of the different microstructures on nonisothermal crystallization and subsequent melting was studied. Using differential scanning calorimetry (DSC) it was observed that samples with lower content of defects showed crystallization on cooling from the melt, and a double melting peak in the subsequent heating scan, the latter associated with melt, recrystallization and remelt processes that it was confirmed by its nonreversing exothermic process found by means of temperature modulated DSC (MDSC). However, polymers with high amount of defects showed cold crystallization on heating followed by a melting process, that it was observed by MDSC. Wide angle X‐ray diffraction was used for characterizing the changes of crystalline forms in relationship with crystallization process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 798–806, 2008

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Currently, to reduce the environmental problems associated with plastic waste, methods are being sought to use this waste as raw materials in different applications, such as fibers. In addition, to improve these materials and provide different properties, nanoparticles (NPs) are incorporated. In the present work, polymeric fibers made of recycled polyethylene terephthalate (r-PET) from post-consumer water bottles, functionalized with 0%, 1.5%, 3% and 6% zinc oxide nanoparticles (ZnO-NPs) in function of r-PET weight, were elaborated to evaluate their antibacterial and antifungal characteristics. The ZnO-NPs were synthesized by the solvothermal method, obtaining particles with a mean diameter of 38.15 nm, while the fibers were obtained by electrospinning with a diameter range between 200–5000 nm. The functionalized fibers were carried out against Escherichia coli and Bacillus subtilis through the agar diffusion method, obtaining the highest inhibition halo at 6% w/w ZnO-NPs, being 26.5 mm and 34.25 mm, respectively. In addition, the same method was used to evaluate the antifungal activity of Penicillium s.p. and Fusarium graminearum, observing antifungal properties due to the presence of nanoparticles in the fibers.

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Revista semestral de la DIUC 43Síntesis y caracterización de nanopartículas magnéticas del tipo Fe 3 O 4 /TiO 2 , efecto del pH en la dispersión y estabilización en soluciones acuosas Fecha de recepción: 17 de octubre 2013 -Fecha de aceptación: 1 de marzo 2014 RESUMENSe sintetizaron nanopartículas magnéticas del tipo Fe 3 O 4 /TiO 2 (núcleo/coraza) mediante el método combinado que involucra para la síntesis inicial del Fe 3 O 4 la co-precipitación química y para la formación de la capa de TiO 2 la síntesis por la técnica sol-gel. Las nanopartículas magnéticas fueron caracterizadas antes y después del proceso de recubrimiento, mediante rayos-X y microscopía electrónica de barrido con emisión de campo y con microanálisis de rayos-X. El análisis de refinamiento estructural se realizó por el método Rietveld a través del programa FullProf, a partir de la difracción de rayos-X de polvo y confirmó la presencia de Fe 3 O 4 como óxido de hierro y que el recubrimiento está constituido por TiO 2 en su fase anastasa. El tamaño del cristal fue calculado mediante la ecuación de Scherrer y corresponde alrededor de 10nm, tanto para el Fe 3 O 4 como para la capa de TiO 2 . Según los análisis de microscopía electrónica de barrido con emisión de campo, las nanopartículas magnéticas recubiertas tienen forma esférica y se encuentran altamente aglomeradas. Los resultados de microscopía electrónica de barrido con microanálisis de rayos-X confirman únicamente la presencia de tres elementos: Fe, Ti y O. Finalmente, la dispersión de las nanopartículas de Fe 3 O 4 /TiO 2 en agua fue evaluada a diferentes valores de pH mediante espectroscopía ultravioleta en el rango del ultravioleta y el visible. Los mayores valores de absorbancia se obtuvieron a pH 8 y 4,5; mostrando una buena dispersión. Por otro lado, a pH 6,5 hay tendencia a aglomerarse con posterior precipitación. Palabras clave: Nanopartículas magnéticas, titania, magnetita, núcleo-coraza, método Rietveld, ecuación de Scherrer. ABSTRACTMagnetic nanoparticles of Fe 3 O 4 /TiO 2 (core/shell) type were synthesized by a method combining chemical co-precipitation for the initial synthesis of Fe 3 O 4 and sol-gel synthesis for the making of the TiO 2 shell film. The magnetic nanoparticles were characterized before and after the coating process by X-ray, field emission scanning electron microscope and scanning electron microscope with X-ray microanalysis. The structural refinement analysis by the Rietveld method was performed through the FullProf program from X-ray powder diffraction, which confirmed the presence of Fe 3 O 4 as iron oxide and the anastase phase of TiO 2 as shell layer. The crystal size was calculated by Scherer's equation and around 10nm for both the Fe 3 O 4 core and TiO 2 shell. According the field emission scanning electron microscope, the coated magnetic nanoparticles are spherical and they are highly agglomerated. The exclusive presence of Fe, Ti and O was confirmed by scanning electron microscope with X-ray microanalysis. Finally, the dispersion of aqueous Fe 3 O 4 /T...

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