The surface of natural Brazilian amazonic fibers (curauá, Ananas erectifolius) was modified with polyaniline nanoparticles, through in situ preparation of polyaniline nanoparticles in presence of the curauá fibers. This allowed for a significant increase in the electrical conductivity of the fibers (≈2 500 times). As the electrical resistivity of the modified fibers is a function of the applied external pressure, the produced composites can be used as a cheap pressure‐sensing material. The modified materials were also characterized by FT‐IR, XPS and SAXS, and the obtained results were used to explain some of the observed characteristics of the materials.magnified image

Cardanol‐furfuraldehyde/maghemite composites were prepared through a bulk polymerization aiming to produce magnetic green resins able to absorb petroleum spilled on the water. Several techniques such as Fourier transform infrared spectroscopy, ultraviolet–visible spectrophotometry, wide angle X‐ray scattering, and small angle X‐ray scattering were used in the characterization of the materials. In addition, magnetic force and oil removal capability tests were also performed. Obtained materials presented a good magnetic force allied with a considerable oil removal capability: each gram of the resin was able to remove 10g of petroleum from the water. Therefore, the easy and simple production process presented is a promising tool for oil spill cleanup process. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

A magnetic resin based on lignin produced using the Kraft process was prepared and characterized. The material, because of its aromatic/aliphatic balance, can be used in oil-spill clean-up processes. The resin was prepared through bulk polycondensation of lignin, cashew nutshell liquid, and formaldehyde in the presence of maghemite nanoparticles. The obtained magnetic composites were studied by Fourier transform infrared spectroscopy, X-ray diffraction, and Small-angle X-ray scattering. Cure degree, magnetic force, and oil removal capability tests were also performed. The results show that the composites possess an elevated cure degree, besides a considerable magnetic force. The materials exhibit a good oil removal capability-the composite containing 3.3 vol % of maghemite can remove 11 parts of oil from water. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 126: E304-E311, 2012

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This work presents the synthesis of micro‐sized polystyrene magnetic beads by in situ incorporation of oleic acid‐modified Fe3O4 magnetic nanoparticles via a suspension polymerization process. Fe3O4 nanoparticles with superparamagnetic characteristics were obtained through a coprecipitation technique. These particles present an average diameter equal to 7.4 ± 4.6 nm, as determined by AFM. This result is in agreement with the crystallite size of single domains calculated by using Scherrer's equation, which was equal to 7.7 nm, based on XRD measurements. The obtained materials were also studied using TGA. The weight loss behavior was independent of the Fe3O4 content and the stability to the thermal degradation was also not improved by magnetic nanoparticles present in the composite. Polystyrene/Fe3O4 magnetic nanocomposites exhibited the same diffraction peaks observed in the pure Fe3O4, which indicates that nanoparticles inside the composites preserved the structure and properties of pure Fe3O4. It was also shown that nanosized polystyrene particles, dispersed in the aqueous phase, are obtained due to the stabilization effect of the oleic acid on the styrene droplets. A cross‐section of polystyrene magnetic particles showed empty spherical regions, attributed to the encapsulation of water microdroplets during the polymerization reaction. The obtained polymeric materials also presented good magnetic behavior, indicating that the modified Fe3O4 nanoparticles were successfully dispersed in the polystyrene particles.

The antibiotic cotrimoxazole was associated with poly(lactic acid-co-glycolic acid) (PLGA) and maghemite, aiming to reach a controlled drug release system. PLGA was synthesized through the polycondensation of lactic acid and glycolic acid in an equimolar ratio, and maghemite was synthesized through the coprecipitation method. The drug cotrimoxazole was inserted in the composite through three different procedures: solution, fusion, and in situ to check the best insertion method. Several techniques were used to characterize the materials. The copolymer was characterized by nuclear magnetic resonance and size-exclusion chromatography. In addition, the maghemite, the composites containing the drug, and the polymer were characterized by Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance device, small-angle X-ray scattering, and magnetic force, this last according to the methodology developed by our group. The root mean square error was used to compare the FTIR spectra of the samples, proving that the fusion method was the best way to insert the drug and maghemite in the polymer. Therefore, composites containing the drug and the nanoparticles were prepared by the fusion method. These composites were used for dissolution profile studies, which were monitored with and without magnetic field, aiming to understand the influence of the magnetic field on the dissolution profile. The dissolution was monitored and quantified using the ultraviolet-visible spectrophotometry, following the United States Pharmacopeia (USP) method for cotrimoxazole tablets. Results demonstrated that nanocomposites presented a good magnetic force, able to keep the magnetic composite trapped in a specific place or tissue. The presence of the nanoparticles in the composites changed the kinetics of the drug release, as they constitute physical barriers to the drug diffusion, contributing to a sustained drug release process. Furthermore, in the presence of a magnetic field, the magnetic nanoparticles were able to perform a magnetic constriction of the material, making the drug release faster than in the absence of the magnetic field, which may be useful to perform a fine tuning of the system, allowing the easier adjustment of the speed and amount of released drug, useful to improve medical treatments and even the welfare of the patients.

No abstract

Cardanol, a well known natural resource, was used to produce a polymer resin in the presence of formaldehyde, catalyzed by H2SO4. Before reticulation, PAni · H2SO4 was blended with the resin. The blended material was cast into poly(propylene) cups and kept inside a desiccator under vacuum until complete water evaporation. The final in situ polymer blend was solid and could not be dissolved in ordinary solvents, indicating that a reticulated material had been obtained. Samples prepared similarly were then characterized, showing that the produced blends can be used as pressure sensing materials.magnified image