Development of a Yellow Pigment Based on Bismuth and Molybdenum-Doped TiO2 for Coloring Polymers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Polyacrylic acid polymers hydrogels intended to topical drug delivery: preparation and characterization

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efficiency comparison of hyperbranched polymers as toughening agents for a one-part epoxy resin

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of biodegradable detergents in the accumulation of lipofuscin (age pigment) in gill and liver of two neotropical fish species

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Escape depth of secondary electrons from electron-irradiated polymers

Measurements on polymers (Teflon FEP and Mylar) have shown that the secondary electron emission from uncharged surfaces exceeds that from surfaces containing a positive surface charge. The reduced emission of charged surfaces is due to recombination between electrons undergoing emission and trapped holes within the charged layer. During the experiments the surface of the material was kept at a negative potential to assure that all secondary electrons reaching the surface from within the material are actually emitted. An analysis of the results yielded the maximum escape depth of the secondary electrons, and showed that the ratio of the maximum escape depth of the secondaries from Mylar to the maximum escape depth from Teflon is almost the same as the ratio of the corresponding second crossover energies of this polymers.

Improvement of the alcohol dehydrogenase from baker's yeast using polymers and salts for alcohol determinations in beverages

An alcohol dehydrogenase (ADH) was purified from dry baker’s yeast. This is a key enzyme of the primary short-chain alcohol metabolism in many organisms. In the present study, the obtained enzymatic preparation of baker’s yeast, containing 2.7 U/mg of ADH, was used in the reactions. The purified extract of the ADH obtained from Fermix commercial dry yeast, presented the highest activity and purification factor when ammonium sulfate was added in the precipitation of protein, in the range 35-60% (w/v). The enzymatic preparation was maintained for 2 months in the lyophilized form at 4ºC (retention of 96.2% of activity) in the presence of 1 mmol/L of sodium azide, and it maintained 47% of activity for 30 days at 30°C in the presence of 15% PEG. The assays of ethanol (detection range 5 mM -150 mM or 2.3 x 10-4 – 6.91 x 10-3g/L) in different samples in alcoholic beverages, presented a maximum deviation of only 2.1%. Assays of recovery of the substrate (99.25%) added in the wine showed that the methodology is viable for this sample type. The standard curve and the analytic curve of this method meet the conditions of precision, sensitivity, simplicity, and low cost, required for a useable analytical method.

Gamma-ray dosimetric properties of conjugated polymers in solution

The effect of gamma radiation on poly{[2,5-bis(3-(N,N-diethylamino)-1-oxapropyl)-1,4-phenylene]-alt-1,4- phenylene} (PPP); poly{[2,5-bis(3-(N,N-diethylammonium bromide)-1-oxapropyl)-1,4-phenylene]-alt-1,4-phenylene} (PPP-Br); and the polymerized dye poly-1-ethyl-2-[3-(1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-ylidene)-1-propenyl]- 3,3-dimethyl-3H-indolium perchlorate (Poly-CyC) has been investigated. The stability and response of poly [2-methoxy- 5-(2'- ethyl-hexyloxy)-p-phenylenevinylene] (MEH-PPV) in mixed solutions have also been explored. To this end, samples with concentrations ranging from 0.005 to 0.500 mg/mL were irradiated with a 60Co gamma-ray source at room temperature, using doses up to 1 kGy, and the response was analyzed by UV-Vis spectroscopy. The obtained results reinforce the previously proposed mechanism and suggest that the effect depends on specific structural characteristics of the main chain of the polymers. Moreover, the polymerized dyes display interesting dosimetric properties. Additionally, it has been noted that, contrary to what happens in other solvents, MEH-PPV is degraded in bromoform solution. Protective effects have also been observed for bromoform+toluene mixtures (1:1 vol/vol) and solutions containing molecular dyes. - See more at: http://www.eurekaselect.com/117251/article#sthash.gHFnYvJk.dpuf

Síntese, caracterização e aplicação de hidrogéis nanoestruturados contendo nanoargila para melhorar a germinação e qualidade de muda de hortaliça

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Understanding the Grafting of Telechelic Polymers on a Solid Substrate to Form Loops

Recent experimental and theoretical studies have demonstrated that relative to singly tethered chains, the presence of polymer loops at interfaces significantly improves interfacial properties such as adhesion, friction, and wettability. In the present study, a simple system was studied to examine the formation of polymeric loops on a solid surface, where the grafting of carboxylic acid terminated telechelic polystyrene from the melt to an epoxy functionalized silicon is chosen. The impact of telechelic molecular weight, grafting temperature, and surface functionality on the telechelic attachment process is studied. It was found that grafting of the telechelic to the surface at both ends to form loops is the primary product of this grafting process. Moreover, examination of the kinetics of the grafting process indicates that it is reaction controlled. Fluorescence tagging of the dangling ends of singly bound chains provides a mechanism to monitor their time evolution during grafting, and these results indicate that the grafting process is accurately described by recent Monte Carlo simulation work. The results also provide a method to control the extent of loop formation at interfaces and therefore provide an opportunity to further understand the role of the loops in the interfacial properties in multicomponent polymer systems.

Charge generation, charge transport, and residual charge in the electrospinning of polymers: A review of issues and complications

Electrospinning has become a widely implemented technique for the generation of nonwoven mats that are useful in tissue engineering and filter applications. The overriding factor that has contributed to the popularity of this method is the ease with which fibers with submicron diameters can be produced. Fibers on that size scale are comparable to protein filaments that are observed in the extracellular matrix. The apparatus and procedures for conducting electrospinning experiments are ostensibly simple. While it is rarely reported in the literature on this topic, any experience with this method of fiber spinning reveals substantial ambiguities in how the process can be controlled to generate reproducible results. The simplicity of the procedure belies the complexity of the physical processes that determine the electrospinning process dynamics. In this article, three process domains and the physical domain of charge interaction are identified as important in electrospinning: (a) creation of charge carriers, (b) charge transport, (c) residual charge. The initial event that enables electrospinning is the generation of region of excess charge in the fluid that is to be electrospun. The electrostatic forces that develop on this region of charged fluid in the presence of a high potential result in the ejection of a fluid jet that solidifies into the resulting fiber. The transport of charge from the charge solution to the grounded collection device produces some of the current which is observed. That transport can occur by the fluid jet and through the atmosphere surrounding the electrospinning apparatus. Charges that are created in the fluid that are not dissipated remain in the solidified fiber as residual charges. The physics of each of these domains in the electrospinning process is summarized in terms of the current understanding, and possible sources of ambiguity in the implementation of this technique are indicated. Directions for future research to further articulate the behavior of the electrospinning process are suggested. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3682464]

Low liquid-solid ratio (LSR) hot water pretreatment of sugarcane bagasse

Low liquid-solid ratio (LSR) can be used to obtain high-content xylo-oligosaccharide (XOS) spend liquor by hot water pretreatment. Developing a technology based on low LSR results in more efficient water usage in the system and thus in lower capital and operating costs. Xylans from xylan rich agro-industrial waste are abundant hemicellulosic polymers with enormous potential for industrial applications. Currently, freeze-dried xylo-oligosaccharides are used as bio-based polymers and hydrolysates containing high xylose contents are converted to several chemical products. In this study, sugarcane bagasse was treated with water at low LSRs and mild temperatures in order to assess the effects of varying the pretreatment conditions on the xylo-oligosaccharide and xylose concentrations, and use a central composite experimental design to optimize the process parameters. The pretreatments were performed in the ranges temperature: 143.3-176.7 degrees C, time: 20-70 min and LSR: 1 : 1 to 11 : 1 (g g(-1)). The maximum concentrations of xylose and xylan were 13.76 and 36.18 g L-1 (equivalent to 48.29 g L-1 of xylan), respectively, which were achieved by treating bagasse at 170 degrees C for 60 min, with LSR of 3 g g(-1). The amount of xylan removed under these conditions was almost 57%. The soluble xylan consisted mainly of xylo-oligosaccharides (74 wt% of the identified compound in the spent liquor).

Hb S-Sao Paulo: A new sickling hemoglobin with stable polymers and decreased oxygen affinity

Hb S-Sao Paulo (SP) [HBB:c.20A > T p.Glu6Val: c.196A > G p.Lys65Glu] is a new double-mutant hemoglobin that was found in heterozygosis in an 18-month-old Brazilian male with moderate anemia. It behaves like Hb S in acid electrophoresis, isoelectric focusing and solubility testing but shows different behavior in alkaline electrophoresis, cation-exchange HPLC and RP-HPLC. The variant is slightly unstable, showed reduced oxygen affinity and also appeared to form polymers more stable than the Hb S. Molecular dynamics simulation suggests that the polymerization is favored by interfacial electrostatic interactions. This provides a plausible explanation for some of the reported experimental observations. (C) 2012 Elsevier Inc. All rights reserved.

Constitutive models for biodegradable thermoplastic ropes for ligament repair

The concept behind a biodegradable ligament device is to temporarily replace the biomechanical functions of the ruptured ligament, while it progressively regenerates its capacities. However, there is a lack of methods to predict the mechanical behaviour evolution of the biodegradable devices during degradation, which is an important aspect of the project. In this work, a hyper elastic constitutive model will be used to predict the mechanical behaviour of a biodegradable rope made of aliphatic polyesters. A numerical approach using ABAQUS is presented, where the material parameters of the model proposal are automatically updated in correspondence to the degradation time, by means of a script in PYTHON. In this method we also use a User Material subroutine (UMAT) to apply a failure criterion base on the strength that decreases according to a first order differential equation. The parameterization of the material model proposal for different degradation times were achieved by fitting the theoretical curves with the experimental data of tensile tests on fibres. To model all the rope behaviour we had considered one step of homogenisation considering the fibres architectures in an elementary volume. (C) 2012 Elsevier Ltd. All rights reserved.

Biocompatible Magnetic Microspheres for Use in PDT and Hyperthermia

Loaded microspheres with a silicon (IV) phthalocyanine derivative (NzPC) acting as a photosensitizer were prepared from polyhydroxybutyrate-co-valerate (PHBHV) and poly(ecaprolactone) (PCL) polymers using the emulsification solvent evaporation method (EE). The aim of our study was to prepare two systems of these biodegradable PHBHV/PCL microspheres. The first one containing only photosensitizer previously incorporated in the PHBHV and poly(ecaprolactone) (PCL) microspheres and the second one with the post magnetization of the DDS with magnetic nanoparticles. Magnetic fluid is successfully used for controlled incorporation of nanosized magnetic particles within the micron-sized template. This is the first time that we could get a successful pos incorporation of nanosized magnetic particles in a previously-prepared polymeric template. This procedure opens a great number of possibilities of post-functionalization of polymeric micro or nanoparticles with different bioactive materials. The NzPC release profile of the systems is ideal for PDT, the zeta potential and the size particle are stable upon aging in time. In vitro studies were evaluated using gingival fibroblastic cell line. The dark citotoxicity, the phototoxicity and the AC magnetic field assays of the as-prepared nanomagnetic composite were evaluated and the cellular viability analyzed by the classical test of MU.

STRATEGIES FOR PREPARATION OF MOLECULARLY IMPRINTED POLYMERS MODIFIED ELECTRODES AND THEIR APPLICATION IN ELECTROANALYSIS: A REVIEW

Molecularly imprinted polymers (MIP's) have been applied in several areas of analytical chemistry, including the modification of electrodes. The main purpose of such modification is improving selectivity; however, a gain in sensitivity was also observed in many cases. The most frequent approaches for these modifications are the electrodeposition of polymer films and sol gel deposits, spin and drop coating and self-assembling of films on metal nanoparticles. The preparation of bulk (body) modified composites as carbon pastes and polymer agglutinated graphite have also been investigated. In all cases several analytes including pharmaceuticals, pesticides, and inorganic species, as well as molecules with biological relevance have been successfully used as templates and analyzed with such devices in electroanalytical procedures. Herein, 65 references are presented concerning the general characteristics and some details related to the preparation of MIP's including a description of electrodes modified with MIP's by different approaches. The results using voltammetric and amperometric detection are described.