Optical Behavior of Conjugated Pt-Containing Polymetallaynes Exposed to Gamma-Ray Radiation Doses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of helium implantation on the properties of plasma polymer films

Polymer films, deposited from acetylene and argon plasma mixtures, were bombarded with 150 keV He+ ions, varying the fluence, Phi, from 10(18) to 10(21) ions/m(2). Molecular structure and optical gap of the samples were investigated by infrared and ultraviolet-visible spectroscopies, respectively. Two-point probe was employed to determine the electrical resistivity while hardness was measured by nanoindentation technique. It was verified modification of the molecular structure and composition of the films. There was loss of H and increment in the concentration of unsaturated carbon bonds with Phi. Optical gap and electrical resistivity decreased while hardness increased with Phi. Interpretation of these results is proposed in terms of chain crosslinking and unsaturation. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Electrical and Optical Properties of Conductive and Transparent ITO@PMMA Nanocomposites

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

The influence of UV-C irradiation on the properties of thermoplastic starch and polycaprolactone biocomposite with sisal bleached fibers

The effect of UV-C irradiation of the TPS and PCL biocomposites with sisal bleached fibers was investigated. The biocomposite was UV-C irradiated at room temperature under air atmosphere. The structural and morphological changes produced when the films were exposed to UV irradiation for 142 h, were monitored using Scanning Electron Microscopy (SEM), Mechanical Tensile Tests, Differential Scanning Calorimetry (DSC), X-ray diffraction, Thermogravimetric analysis (TGA), and Fourier transform infra-red analysis (FTIR). Addition of 5-10% fibers in composites exhibited improved mechanical and thermal properties attributed to more efficient dispersibility of fiber in the matrix and good compatibility between fibers and the matrix polymer, however, after irradiated, the tensile properties decreased due to chain scission. The samples of irradiated PCL and IFS showed crystallinity increase, whereas the blend and composites showed a decrease in crystallinity. The DSC and X-ray diffraction studies suggested interaction between polymers in the blend via carboxyl groups in thermoplastic starch-PCL and hydroxyl groups in fibers. (C) 2011 Elsevier Ltd. All rights reserved.

Optical and Structural Properties of Zein-Xanthan Gum Biofilms

Structural and optical characteristics of zein-based films produced with different xanthan gum concentrations have been studied in this work. Scanning electronic microscopy (SEM) and optical microscopy (OM) were performed to identify if the incorporation of the material into the matrix film, formed a homogeneous structure, as well as to characterize its constituents as the colour and shape. SEM showed a homogeneous matrix for the control (0% xanthan) with good lipid distribution. However, when the samples were investigated by OM, lipids globules in the control biofilm appeared larger and more dispersed in the matrix than the others samples. Transparency/opacity test measurements by UV-VIS analysis indicated that the addition of xanthan to the film matrix lowered significantly its transparency properties Overall, the addition of xanthan gum favoured lipid dispersion in the matrix, making biomaterials more homogeneous, although with less transparency.

Manipulation of anchoring strength in an azo-dye side chain polymer by photoisomerization

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

RELATIONSHIPS BETWEEN THE PLASMA ENVIRONMENT AND THE COMPOSITION AND OPTICAL-PROPERTIES OF PLASMA-POLYMERIZED THIN-FILMS PRODUCED IN RF DISCHARGES OF C2H2-SF6 MIXTURES

Polymer films were grown in rf discharges containing different proportions of C2H2 and SF6. Quantitative optical emission spectrometry (actinometry) was used to follow the trends in the plasma concentrations of the species H and F, and more tentatively, of CH, CF, and CF2, as a function of the feed composition. Infrared spectroscopy revealed the density of CH and CF bonds in the deposited material. As the partial pressure of SF6 in the feed was increased, the degree of fluorination of the polymer also rose. The form of the dependency of the deposition rate on the proportion of SF6 in the feed was in good qualitative agreement with the activated growth model. From transmission ultraviolet visible spectroscopy data the refractive index and the absorption coefficient of the polymers were calculated as a function of the deposition parameters. Since the optical gap depended to some extent upon the degree of fluorination, it could, within limits, be determined by a suitable choice of the proportion of SF6 in the feed. A qualitative explanation of this relationship is given.

FLUORINATED POLYMER-FILMS FROM RF PLASMAS CONTAINING BENZENE AND SULFUR HEXAFLUORINE

Mixtures of C6H6 and SF6 were polymerized in an r.f. discharge. Actinometry (quantitative optical emission spectroscopy) was used to determine trends in the plasma concentrations of the species F, H and CH as a function of the proportion of SF6 in the feed. Infrared spectroscopy and electron spectroscopy for chemical analysis were employed to characterize the deposited material. Increasing proportions of SF, in the feed produced increased fragmentation of the benzene molecules and greater fluorination of the deposited material. The deposition rate, as determined by optical interferometry, was found to be enhanced about 4 times by the presence of 10-20% SF6 in the feed. At 50% SF6 in the feed, deposition rates were greater than in pure C6H6 plasmas despite the (probably large) etching effect of atomic fluorine from the discharge. Relationships between the plasma composition, electron density and temperature, film composition and growth rate are discussed.

An ultra stable glass system for optical fiber devices

In this paper a modified chalcogenide glass was studied by X-ray powder diffraction, differential thermal analysis, infrared and Raman scattering spectroscopies. The study of this new matrix opens new perspectives to fabricate Pr3+-doped fibers to operate as an optical amplifier in the 1.3 mum telecommunications window. The Pr3+-doped 70Ga(2)S(3)-30La(2)S(3) glass was modified through the substitution of La2S3 by La2O3, which improves the thermal stability of these glasses without any modification of phonon energy. The possibility to pull a fiber from this glass system without any devitrification is easily achieved.

The effect of N+ ion energy on the properties of ion bombarded plasma polymer films

This work describes the influence of the ion bombardment on the electrical, optical and mechanical properties of polymer films deposited from radio-frequency plasmas of benzene. Irradiations were conducted using N+ at 5 x 10(19) ions/m(2), varying the ion energy, E-0, from 0 to 150 keV. Film elemental composition was determined by Rutherford backscattering spectroscopy. Electrical resistivity and hardness were obtained by the two-point probe and nanoindentation technique, respectively. Ultraviolet-visible spectroscopy was employed to investigate the optical constants of the samples. Etching rate was determined by exposure of the films to reactive oxygen plasmas. Ion bombardment induced gradual loss of H and increase in C and O concentrations with Eo. As a consequence the electrical, optical and mechanical properties were drastically affected. Interpretation of these results is proposed in terms of chain cross-linking and unsaturation. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Oxygen plasma treatment of sisal fibers and polypropylene: Effects on mechanical properties of composites

Polypropylene powder and sisal fibers were oxygen plasma treated, and the mechanical properties of their composites were tested. Two main effects were investigated: the incorporation of oxygen polar groups in the polypropylene surface and the surface degradation and chain scission of both polypropylene and sisal fibers. Prior to these treatments, three reactor configurations were tested to investigate the best condition for both effects to occur in PP film. Results showed that polypropylene-cellulose adhesion forces are about an order of magnitude higher for PP film treatments at 13.56 MHz than at 40 kHz owing to much higher chain scission at lower frequencies, although it probably also occurs at high frequency and high power. Polypropylene powder treated with oxygen plasma in optimum conditions for polar group incorporation did not result in improvement in any composite mechanical property, probably owing to the polymer melting. Sisal fibers and PP powder treated In conditions of surface degradation did not improve flexural or tensile properties but resulted in higher impact resistance, comparable to the improvement obtained with the addition of compatibilizer.

Optical, electrical, and thermochromic properties of polyazothiophene Langmuir-Blodgett films

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

Morphological, mechanical properties and biodegradability of biocomposite thermoplastic starch and polycaprolactone reinforced with sisal fibers

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

Pineapple Leaf Fibers for Composites and Cellulose

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Optical chemical sensors using polythiophene derivatives as active layer for detection of volatile organic compounds

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