Análisis de las relaciones morfología-propiedades en nanocompuestos basados en matrices de copolímeros de bloque

El objetivo principal de la presente investigación ha sido desarrollar una nueva clase de materiales nanocompuestos orgánicos-inorgánicos basados en la capacidad de los copolímeros de bloque de auto-organizarse promoviendo la dispersión de nanopartículas, así como relacionar las diferentes morfologías obtenidas con las propiedades finales de los nanocompuestos. Para generar la nanoestructuración de estos nanocompuestos basados en copolímeros de bloque, como el poli(estireno-b-isopreno-b-estireno) (SIS) y el poli(estireno-b-butadieno-b-estireno) (SBS) en nanopartículas de plata, se han utilizado los conceptos de compatibilización y confinamiento. Es decir, las nanopartículas inorgánicas se confinaron en una sola fase del copolímero de bloque mediante tratamientos superficiales y su funcionalización física. En particular, se utilizaron surfactantes (el cloruro de tetrametilamonio, TMAC, y el dodecanotiol, DT) para favorecer la interacción entre las nanopartículas inorgánicas y la matriz polimérica. Teniendo en cuenta los cálculos teóricos de los parámetros de solubilidad obtenidos mediante la teoría de Hoftizer-Van Krevelen, y la electronegatividad propia de los diferentes elementos, los dos surfactantes elegidos tienen una muy buena compatibilidad con el bloque de estireno favoreciendo la localización de las nanopartículas de plata en este bloque.

Atmospheric PM and volatile organic compounds released from Mediterranean shrubland wildfires

Wildfires produce a significant release of gases and particles affecting climate and air quality. In the Mediterranean region, shrublands significantly contribute to burned areas and may show specific emission profiles. Our objective was to depict and quantify the primary-derived aerosols and precursors of secondary particulate species released during shrubland experimental fires, in which fire-line intensity values were equivalent to those of moderate shrubland wildfires, by using a number of different methodologies for the characterization of organic and inorganic compounds in both gas-phase and particulate-phase. Emissions of PM mass, particle number concentrations and organic and inorganic PMx components during flaming and smouldering phases were characterized in a field shrubland fire experiment. Our results revealed a clear prevalence of K+ and SO42- as inorganic ions released during the flaming-smouldering processes, accounting for 68 to 80% of the inorganic soluble fraction. During the residual-smouldering phases, in addition to K+ and SO42-, Ca2+ was found in significant amounts probably due the predominance of re-suspension processes (ashes and soil dust) over other emission sources during this stage. Concerning organic markers, the chromatograms were dominated by phenols, n-alkanals and n-alkanones, as well as by alcohol biomarkers in all the PMx fractions investigated. Levoglucosan was the most abundant degradation compound with maximum emission factors between 182 and 261 mg kg-1 in PM2.5 and PM10 respectively. However, levoglucosan was also observed in significant amounts in the gas-phase. The most representative organic volatile constituents in the smoke samples were alcohols, carbonyls, acids, monocyclic and bicyclic arenes, isoprenoids and alkanes compounds. The emission factors obtained in this study may contribute to the validation and improvement of national and international emission inventories of this intricate and diffuse emission source.

Electrocatalytic oxidation of ascorbic acid on mesostructured SiO2-conducting polymer composites

The conducting self-doping copolymer poly(aniline-co-ABA) preserves its redox activity at pH values as high as 7. This observation was the starting point to synthesize an organic–inorganic hybrid composite able to electrochemically oxidize ascorbic acid molecules at that pH. The inorganic part of the catalytic element was an ordered mesoporous electrodeposit of SiO2, which has been used as the template for the electrochemical insertion of the self-doping copolymer. The oxidation of ascorbate ions at a fixed potential on this composite was studied by means of the kinetic model proposed by Bartlett and Wallace (2001). It was observed that the effective kinetic constant KME increased significantly but, simultaneously, k′ME remained almost constant when the composite was employed as the electrocatalytic substrate. These results were interpreted in the light of two combinations of kinetic constants, which strongly suggested that the increase in KME should be ascribed to the improvement in electronic conductivity of the copolymer induced by the highly ordered silica template.