Desenvolvimento e caracterização de dispositivos de visualização eletroluminescentes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Produção e caracterização de micro e nanofibras de Poli(fluoreto de vinilideno) - PVDF obtidos pela técnica de fiação por sopro em solução

Pós-graduação em Ciência dos Materiais - FEIS

Estudo das propriedades térmicas e mecânicas de blendas de PVDF/PANI

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de biomateriais a partir de blendas poliméricas a base de amido

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fabricação e caracterização estrutural de filmes de materiais poliméricos visando a aplicação como biomateriais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e caracterização de compósitos poli(fluoreto de vinilideno-trifluoretileno)/titanato de bário para uso em regeneração tecidual guiada

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biomaterials from blends of fluoropolymers and corn starch-implant and structural aspects

The development of polymeric blends to be used as matrices for bone regeneration is a hot topic nowadays. In this article we report on the blends composed by corn starch and poly(vinylidene fluoride), PVDF, or poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), to obtain biocompatible materials. Blends were produced by compressing/annealing and chemically/structurally characterized by micro-Raman scattering and Fourier transform infrared (FTIR) absorption spectroscopies, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM), besides in vivo study to evaluate the tissue response. Vibrational spectroscopy reveals no chemical interaction between the polymers and starch, absence of material degradation due to compressing/annealing process or organism implantation, and maintenance of a and ferroelectric crystalline phases of PVDF and P(VDF-TrFE), respectively. As a consequence of absence of interaction between polymers and starch, it was possible to identify by SEM each material, with starch acting as filler. Elastic modulus (E') obtained from DMA measurement, independent of the material proportion used in blends, reaches values close to those of cancellous bone. Finally, the in vivo study in animals shows that the blends, regardless of the composition, were tolerated by cancellous bone. (C) 2013 Elsevier B.V. All rights reserved.

Measurement of Radiant Energy using Pyroelectric Polymer/Ceramic Composite

Monitoring non-ionizing radiant energy is increasingly demanded for many applications such as automobile, biomedical and security system. Thermal type infrared (IR) sensors can operate at room temperature and pyroelectric materials have high sensitivity and accuracy for that application. Working as thermal transducer pyroelectric sensor converts the non-quantified thermal flux into the output measurable quantity of electrical charge, voltage or current. In the present study the composite made of poly(vinylidene fluoride) -PVDF and lead zirconate titanate (PZT) partially recovered with polyaniline (PAni) conductor polymer has been used as sensor element. The pyroelectric coefficient p(T) was obtained by measuring the pyroelectric reversible current, i.e., measuring the thermally stimulated depolarization current (TSDC) after removing all irreversible contribution to the current such as injected charge during polarization of the sample. To analyze the sensing property of the pyroelectric material, the sensor is irradiated by a high power light source (halogen lamp of 250 W) that is chopped providing a modulated radiation. A device assembled in the laboratory is used to change the light intensity sensor, an aluminum strip having openings with diameters ranging from 1 to 10 mm incremented by one millimeter. The sensor element is assembled between two electrodes while its frontal surface is painted black ink to maximize the light absorption. The signal from the sensor is measured by a Lock-In amplifier model SR530 -Stanford Research Systems. The behavior of the output voltage for an input power at several frequencies for PZT-PAni/PVDF (30/ 70 vol%) composite follows the inverse power law (1/ f) and the linearity can be observed in the frequency range used.

Fabrication and Characterization of PZT-PAni/PVDF Based Nanocomposite

This work presents the preparation and characterization of PZT ceramic obtained by the polymeric precursor method (PPM). The influence of the synthesis method on the grain size and the morphology are also object of study. The fabrication and characterization of composite films with 0-3 connectivity, immersing nanoparticles of PZT into the non-polar poly(vinylidene fluoride) -PVDF as the polymer matrix were presented. For comparison there are results obtained with composite samples made of ceramic particles unrecovered and recovered with a conducting polymer, the polyaniline (PAni).

Preparo e caracterização de compósitos polímero/cerâmica com potencial aplicação como sensor multifuncional

Pós-graduação em Química - IQ

Desenvolvimento e caracterização de dispositivos eletroluminescentes contendo uma blenda polimérica condutora e Zn2SiO4:Mn

Despite the great development of organic and polymeric electroluminescent materials, the large scale commercial application of devices made with these materials seems conditioned to specific cases, mainly due to the high cost and the low durability, in compared to conventional technologies. In this study was produced electroluminescent devices by a process simple, drop casting. Were produced electroluminescent films containing Zn2SiO4:Mn immersed in a conductive polymer blend with different thicknesses. The morphological characteristics of these films were studied by scanning electronic microscopy. These films were used in the manufacture of electroluminescent devices, in which the light emission properties of the developed material were evaluated. The blend was composed of the conductive polymer Poly(o-methoxyaniline), doped with p-toluene sulfonic acid, and an insulating polymer, Poly(vinylidene fluoride) and its copolymer Poly(vinylidene fluoride-cotrifluoroethylene). To this blend was added Zn2SiO4:Mn, thereby forming the composite. A first set of devices was obtained using composites with different weight fraction of polymeric and inorganic phases, which were deposited by drop casting over ITO substrates. Upper electrodes of aluminum were deposited by thermal evaporation. The resulting device architecture was a sandwich type structure ITO/ composite/ Al. A second set of devices was obtained as self-sustaining films using the best composite composition obtained for the device of the first set. ITO electrodes were deposited by RF-Sputtering, in both faces of these films. The AC electrical characterization of the devices was made with impedance spectroscopy measurements, and the DC electrical characterization was performed using a source/ meter unit Keithley 2410. The devices light emission was measured using a photodiode coupled to a digital electrometer, Keithley 6517A. The devices electrooptical characterization showed that the...

Obtenção e caracterização de mantas fibrosas de poli(fluoreto de vinilideno) (PVDF) com poli(o-metoxianilina) (POMA) pela técnica de "Solution Blow Spinning"

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The Synthesis and properties of functionalised polymers

The aim of this project was to synthesise fluorinated polymers that might act as hot material in a guest-host system for use in non-linear optical applications. These polymers would be expected to have the advantage over materials such as poly(vinylidene fluoride) which is known to be incompatible with many nlo active materials. A series of bicyclic fluorinated monomers was prepared by the reaction of fluorinated dienophiles with cyclopentadiene in a series of Diels-Alder reactions. The monomers were purified and then used in ring opening metathesis polymerisation. The materials were then characterised by gel permeation chromatography and nuclear magnetic resonance spectroscopy and cast as films for determination of their activities as nlo materials using a Nd/YAG laser system. The second harmonic intensity of each was measured relative to quartz. However no materials of significant activity were produced. In an attempt to produce polymers that might subsequently be functionalised the polymerisation of 1,2-methylenedioxybenzene and 1,4-benzodioxane was investigated.

Nanostructured smart materials as functional components of medical devices

The field of medical devices has experienced, more than others, technological advances, developments and innovations, thanks to the rapidly expanding scientific knowledge and collaboration between different disciplines such as biology, engineering and materials science. The design of functional components can be achieved by exploiting composite materials based on nanostructured smart materials, that due to the inherent characteristics of single constituents develop unique properties that make them suitable for different applications preserving excellent mechanical proprieties. For instance, recent developments have focused on the fabrication of piezoelectric devices with multiple biomedical functions, as actuation and sensing functions in one component for monitoring pressure signals. The present Ph.D. Thesis aims at investigating nanostructured smart materials embedded into a polymeric matrix to obtain a composite material that can be used as a functional component for medical devices. (i) Nanostructured piezoelectric material with self-sensing capability was successfully manufactured by using ceramic (i.e. lead zirconate titanate (PZT)) and (ii) polymeric (i.e. poly(vinylidene fluoride-trifluoro ethylene (PVDF-TRFE)) piezoelectric materials. PZT nanofibers were obtained by sol-gel electrospinning starting from synthetized PZT precursor solution. Synthesis, sol-gel electrospinning process, and thermal treatment were accurately controlled to obtain PZT nanofibers dimensionally stable with densely packed grains in the perovskite phase. To guarantee the impact resistance of the laminate, the morphology and size of the hosting filler were accurately designed by increasing the surface area to volume ratio. Moreover, to solve the issue relative to the mechanical discrepancy between rigid electronic materials/soft human tissues/different material of the device (iii) a nanostructured flexible composite material based on a network of Poly-L-lactic acid (PLLA) made of curled nanofibers that present a tuneable mechanical response as a function of the applied stress was successful fabricated.

Three-layer piezoelectrets from fluorinated ethylene-propylene (FEP) copolymer films

A process for preparing three-layer piezoelectrets from fluorinated ethylene-propylene (FEP) copolymer films is introduced. Samples are made from commercial FEP films by means of laser cutting, laser bonding, electrode evaporation, and high-field poling. The observed dielectric-resonance spectra demonstrate the piezoelectricity of the FEP sandwiches. Piezoelectric d (33) coefficients up to a few hundred pC/N are achieved. Charging at elevated temperatures can increase the thermal stability of the piezoelectrets. Isothermal experiments for approximately 15 min demonstrate that samples charged at 140A degrees C keep their piezoelectric activity up to at least 120A degrees C and retain 70% of their initial d (33) even at 130A degrees C. Acoustical measurements show a relatively flat frequency response in the range between 300 Hz and 20 kHz.