Poli (metil azoteto de glicidila) - GAP. I: síntese e caracterização

O poli (metil azoteto de glicidila) - GAP - é um material energético que pode ser utilizado como aglutinante (binder) e como plastificante energético em compostos explosivos e propulsores de foguetes. Neste trabalho, foi abordada a síntese do (GAP) através da conversão direta da epicloridrina (ECH) a GAP. Os reagentes utilizados foram azida de sódio, epicloridrina e vários álcoois extensores de cadeias, o etanodiol, o 1,4-butanodiol, o dietilenoglicol e o glicerol. Alguns parâmetros de operação foram avaliados, como o tempo de reação, a proporção entre os reagentes, dois tipos de solvente e a ordem de adição dos reagentes. A variável observada para a análise foi a massa molecular do GAP. Todos os materiais sintetizados também foram caracterizados por análises de FTIR, UV, RMN, DSC, análise elementar e TGA. Uma maior massa molecular, maior rendimento e uma melhor conversão do grupo azida a GAP foram obtidos com a adição de epicloridrina sobre a azida de sódio e usando DMF como solvente.

Poli (metil azoteto de glicidila) - GAP. II: mecanismo de reação

O poli (metil azoteto de glicidila) - GAP - é um material energético que pode ser utilizado como aglutinante (binder) e como plastificante energético em compostos explosivos e propulsores de foguetes. O GAP de baixo peso molecular pode ser obtido pela conversão direta da epicloridrina (ECH) a GAP. Neste trabalho, é proposto um possível mecanismo para esta conversão direta, fundamentado em análises de infravermelho de espécies intermediárias.

Effect of Prior Photodegradation on the Biodegradation of Polypropylene/Poly(3-hydroxybutyrate) Blends

In this work, the effect of blend composition and previous photodegradation on the biodegradation of polypropylene/ poly(3-hydroxybutyrate) (PP/PHB) blends was studied. The individual polymers and blends with or without the addition of poly(ethylene-co-methyl acrylate- co-glycidyl methacrylate) [P(E-MA-GMA)] as a compatibilizer (in the case of 80/20 blend) were exposed to UV light for 4 weeks and their biodegradation was evaluated. The biodegradation of PHB phase within the blends was hindered as PHB was the dispersed phase and PP fibrous particles were observed at the surface of the blend samples after biodegradation. Previous photodegradation lessened PHB biodegradation but enhanced the biodegradation of PP and the blends within the biodegradation time studied. Photodegradation resulted in cracks at the surface of PP and the blends, which probably facilitated the biotic reactions due to an easier access of the enzymes to deeper polymer layers. It also resulted in a decrease of molecular weight of PP phase and formation of carbonyl and hydroxyl groups which were consumed during biodegradation. Size exclusion chromatography analysis revealed that only the short chains of PP were consumed during biodegradation.

Effect of EVA on the fresh properties of cement paste

The improved workability effect of latex in dry mortars has not been fully clarified. The purpose of this research was to investigate the influence of the EVA copolymer on the cement hydration and on the rheological properties of cement pastes. The results pointed to a minor influence of EVA on cement hydration and to a ball-bearing effect. In fact, the shear thinning behavior of reference paste at 15 min after mixing changed to shear thickening owing to the EVA addition. This behavior could be explained by the decrease in the interparticle separation distance as consequence of the solid content increase in case of shearing detachment of weakly adhered EVA particles from the cement particles surfaces. The expected EVA plasticizing effect was observed at 60 min. Such behavior points to the stabilization of EVA on the cement particles surfaces, thus resulting in a steric barrier effect.

PVC orientado-avaliação de processo de orientação e das propriedades mecânicas em função da razão de estiramento

Este artigo avalia o efeito da "orientação molecular" nas propriedades mecânicas do PVC Rígido. Introduz-se o tema associando-o à aplicação do PVC Orientado em sistemas de tubulações, considerando a importância do nível de gelificação na qualidade desses produtos. É descrito e testado um método experimental de orientação mono-axial em um extrudado e materiais com diferentes razões de estiramento são produzidos para avaliação de propriedades mecânicas. Aumentando a razão de estiramento, há ganhos principalmente no limite de resistência à tração, além do módulo elástico sob tração e tenacidade. Por outro lado, a deformação na ruptura é reduzida.

Optical storage in azobenzene-containing epoxy polymers processed as Langmuir Blodgett films

In this study, azocopolymers containing different main-chain segments have been synthesized with diglycidyl ether of bisphenol A (DGEBA, DER 332, n=0.03) and the azochromophore Disperse Orange 3 (DO3) cured with twomonoamines, viz. benzylamine (BA) and m-toluidine (MT). The photoinduced birefringence was investigated in films produced with these azopolymers using the spin coating (SC) and Langmuir Blodgett (LB) techniques. In the LB films, birefringence increased with the content of azochromophore and the film thickness, as expected. The nanostructured nature of the LB films led to an enhanced birefringence and faster dynamics in the writing process, compared to the SC films. In summary, the combination of azocopolymers and the LBmethod may allow materials with tuned properties for various optical applications, including in biological systems were photoisomerization may be used to trigger actions such as drug delivery.

Femtosecond laser processing of glassy and polymeric matrices containing metals and semiconductor nanostructures

Tailoring properties of materials by femtosecond laser processing has been proposed in the last decade as a powerful approach for technological applications, ranging from optics to biology. Although most of the research output in this field is related to femtosecond laser processing of single either organic or inorganic materials, more recently a similar approach has been proposed to develop advanced hybrid nanomaterials. Here, we report results on the use of femtosecond lasers to process hybrid nanomaterials, composed of polymeric and glassy matrices containing metal or semiconductor nanostructures. We present results on the use of femtosecond pulses to induce Cu and Ag nanoparticles in the bulk of borate and borosilicate glasses, which can be applied for a new generation of waveguides. We also report on 3D polymeric structures, fabricated by two-photon polymerization, containing Au and ZnO nanostructures, with intense two-photon fluorescent properties. The approach based on femtosecond laser processing to fabricate hybrid materials containing metal or semiconductor nanostructures is promising to be exploited for optical sensors and photonics devices.

Determination of degree of ionization of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy‑4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) in layer-by-layer films using vacuum photoabsorption spectroscopy

Electrostatic and hydrophobic interactions govern most of the properties of supramolecular systems, which is the reason determining the degree of ionization of macromolecules has become crucial for many applications. In this paper, we show that highresolution ultraviolet spectroscopy (VUV) can be used to determine the degree of ionization and its effect on the electronic excitation energies of layer-by-layer (LbL) films of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy-4 hydroxyphenylazo)- benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO). A full assignment of the VUV peaks of these polyelectrolytes in solution and in cast or LbL films could be made, with their pH dependence allowing us to determine the p'K IND. a' using the Henderson-Hasselbach equation. The p'K IND. a' for PAZO increased from ca. 6 in solution to ca. 7.3 in LbL films owing to the charge transfer from PAH. Significantly, even using solutions at a fixed pH for PAH, the amount adsorbed on the LbL films still varied with the pH of the PAZO solutions due to these molecular-level interactions. Therefore, the procedure based on a comparison of VUV spectra from solutions and films obtained under distinct conditions is useful to determine the degree of dissociation of macromolecules, in addition to permitting interrogation of interface effects in multilayer films.

Electrochemically prepared polypyrrole-2-carboxylic acid films: synthesis protocols and studies on biosensors

The process for obtaining polypyrrole-2-carboxylic acid (PPY-2-COOH) films in acetonitrile was investigated using cyclic voltammetry, electrochemical quartz crystal microgravimetry (EQCM), and infrared spectroscopy (FTIR). Different potential ranges were applied during cyclic voltammetry experiments with the aim of obtaining films without and with the presence of controlled amounts of water added in acetonitrile. The FTIR spectra of the films have evidenced that cations and anions from the electrolyte solution were incorporated into the PPY-2-COOH structure, with a preferential adsorption of cations. After chemically immobilizing polyphenoloxidase (tyrosinase, PPO), PPY-2-COOH/PPO films were build for amperometric detection of catechol, establishing a linear limit of concentrations ranging from 5.0 x 10-4 to 2.5 x 10-2 mol L-1.

Molecular dynamics of poly(Ethylene Glycol) intercalated in clay, studied using 13C solid-state NMR

In this study, Cross-Polarization Magic-angle Spinning CP/MAS, 2D Exchange, Centerband-Only Detection of Exchange (CODEX), and Separated-Local-Field (SLF) NMR experiments were used to study the molecular dynamics of poly(ethylene glycol) (PEG) inside Hectorite/PEG intercalation compounds in both single- and double-layer configurations. The results revealed that the overall amplitude of the motions of the PEG chain in the single-layer configuration is considerably smaller than that observed for the double-layer intercalation compound. This result indicates that the effect of having the polymer chain interacting with both clay platelets is to produce a substantial decrease in the motional amplitudes of those chains. The presence of these dynamically restricted segments might be explained by the presence of anchoring points between the clay platelets and the PEG oxygen atoms, which was induced by the Na+ cations. By comparing the PEG motional amplitudes of the double-layered nanocomposites composed of polymers with different molecular weights, a decrease in the motional amplitude for the smaller PEG chain was observed, which might also be understood using the presence of anchoring points.

Effect of a polymeric protective coating on optical and electrical properties of poly (p-phenylene vinylene) derivatives

The resistance to photodegradation of poly [(2-methoxy-5-n-hexyloxy)-p-phenylene vinylene] (OC1OC6-PPV) films was significantly enhanced by the use of poly(vinyl alcohol) 99% hydrolyzed as protective coating. The deposition of poly(vinyl alcohol) onto OC1OC6-PPV films did not affect the absorption and the emission spectra of the luminescent polymer. The protected film showed 5% drop on the absorbance at 500nm after 270 hours of light exposure while the unprotected film completely degraded in the same conditions. The conductivity of the protected film remained stable (around 7 × 10-10 S/m) while the value for the unprotected one dropped around two orders of magnitude after 100 hours of light exposure.

Synthesis and photovoltaic performance of a fluorene-bithiophene copolymer

We present the synthesis of a copolymer structure, poly(9,9′-n-di-hexyl-2,7-fluorene-alt-2,5- bithiophene), referred to herein as LaPPS43, and its physico-chemical characterization. Thin films of this polymer mixed with phenyl-C61-butyric acid methyl ester (PCBM) were used as the active layer in photovoltaic devices using the ITO/PEDOT:PSS/LaPPS43: PCBM/Ca/Al bulk heterojunction structure. The devices of different active layer thicknesses were electrically studied using J-V curves and the Photo-Celiv technique. The obtained results show that LaPPS43 combined with PCBM is a promising system for photovoltaic devices. Device performance is discussed in terms of the mean drift distance x for charge carriers. Photophysical data showed that the excitonic species are all localized in the aggregated forms. The mechanism of exciton formation and dissociation is also discussed.

Ecology of marine bacteroidetes: a genomics approach

Institut de Ciències del Mar (ICM-CSIC). Doctorado en oceanografía. Con mención de Calidad de la ANECA

Energeia Año 13 Nº 13, 2015 (número completo)

Contenido: Presentación -- Desarrollo de una nueva técnica de base colorimétrica para una rápida evaluación de la biodegradabilidad de materiales polímeros / M. L. Burdisso ; L. M. Salvatierra ; L. M. Pérez -- Evaluación de los mecanismos de eliminación de Pb2+ en sistemas de fitorremediación en lotes operados con Salvinia biloba raddi (acordeón de agua) / W. Tello Zevallos ; L. M. Salvatierra ; L. M. Pérez -- Estudio a escala laboratorio y planta piloto, de la adsorción de NO y SO2 sobre CR2O3/AL2O3 a altas temperaturas, provenientes de fuentes fijas / Ignacio D. Coria ; Oscar Carattoli, Sabrina Hernández Guiance ; Diana Hamann -- Monitoreo de condiciones de higiene y seguridad del ambiente en entornos industriales usando redes de sensores inalámbricos / Eduardo Rodríguez ; Claudia Deco ; Luciana Burzacca ; Mauro Pettinari ; Santiago Costa ; Cristina Bender -- Análisis de la eficiencia técnica de programas de desarrollo empresarial : avance de investigación II / Luis Piacenza ; Pablo Salvático ; Azul Chamorro -- Estudio de los procesos de transferencia de masa, cantidad de movimiento y energía en el secado de granos de origen agrícola : desarrollo de herramientas de cálculo aplicables al diseño de equipos y control de procesos / Guillermo Boffa ; Francisco Casiello ; Ana María Farias ; Oscar Galaretto ; Fernando Giannico ; Luis Herrera -- Marginalidad urbana y organizaciones de la sociedad civil en el barrio San Francisquito de la ciudad de Rosario, Santa Fe, Argentina / Carlos Fernández ; María Elena Aradas Díaz -- Construyendo la memoria del barrio San Francisquito / Graciela Enria -- Análisis desde la ingeniería ambiental dsobre la problemática de recuperar plásticos desechados los cuales son incorporados a materiales o elementos constructivos en una vivienda económica como respuesta socio-ambiental / A. Espinosa ; J. L. Parodi ; A. D'Alleva ; S. Forestieri ; M. Avendaño ; V. Bitteti -- Cuantificación de la capltura de CO2 por la flora nativa de totora en un humedal costero de Perú / H. Pérez Pinedo ; E. Luccini ; L. Herrera ; M. Parodi ; M. Matar ; L. Barrea ; M. Mechni ; E. Masramón

Ensayos toxicológicos de retardantes de flama polibromados (PBDEs) sobre el caracol manzana

Los éteres de difenil polibromados (PBDEs), son un grupo de compuestos químicos industriales que pertenecen a la familia de los retardantes de llama bromados (BFRs) y comprenden 209 congéneres en función del número de bromos asociados y su posición. Estas sustancias son agregadas a los polímeros presentes en las placas electrónicas, computadoras, televisores, automóviles y aeronaves, entre otros, para inhibir o retardar el inicio y propagación del fuego. El congénere BDE-209 es uno de los PBDEs más utilizado. Su importancia reside en que son agregados a múltiples plásticos, de los cuales se liberan fácilmente, causando efectos negativos en el ambiente y en la salud humana. Su producción está regulada por la Convención de Estocolmo por ser contaminantes orgánicos persistentes (POPs por sus siglas en inlgés). El caracol manzana, Pomacea canaliculata, (Caenogastrópodo de la familia Ampullariidae) ha sido propuesto como un bioindicador de POPs. En este trabajo se expuso a dicha especie a la exposición a corto plazo del congénere BDE-209, en tres concentraciones diferentes (400 (C1), 4700 (C2) y 8300 (C3) μg g-1 de lípido) durante 42 días. Durante dicho tiempo todos los animales sobrevivieron al tratamiento. Se registró un aumento, no significativo, en la frecuencia de las cópulas en el tratamiento C3. El porcentaje de huevos embrionados entre tratamientos no arrojó diferencias significativas para ninguna de las concentraciones ensayadas. Sin embrago el registro de puestas mostró una disminución significativa para la concentración C2. Para esta última concentración se observó una alteración en la coloración de los huevos, cuyos valores fueron registrados empleando un espectroradiómetro. No se observaron diferencias entre los tratamientos a nivel histológico. Los resultados del presente trabajo son alentadores para explorar eventuales mecanismos de detoxificación que protejan a Pomacea canaliculata del BDE-209.