Navegando por Palavras-chave "Polymer blends"

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    Correlation between the PL and EL emissions of polyfluorene-based diodes using bilayers or polymer blends
    (Elsevier Science Sa, 2017) de Azevedo, Diego; Freitas, Jilian Nei; Domingues, Raquel Aparecida [UNIFESP]; Faleiros, Marcelo Meira; Atvars, Teresa Dib Zambon
    The electroluminescent (EL) properties of two polyfluorene-based (poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT)) organic light-emitting diodes (OLEDs) were investigated. Two diode configurations were tested: blends with emissive layers of PFO (higher weight percentage, from 98 to 99.8 wt.%) and F8BT (lower weight percentage, from 0.2 to 2 wt.%) and bilayers of PFO/F8BT. To understand the diode performances, we compared the photoluminescence (PL) and the EL emissions of both configurations. PL emission decays showed that the fluorescence resonant energy transfer (FRET) efficiency is higher for blends that have less of the F8BT component than in bilayers. For the bilayer systems, however, the FRET efficiency is approximately 50%, confirming the significant inter-penetration of these two polymers. Upon decreasing the F8BT concentration in the blend or the F8BT film thickness in the bilayer, the EL emission shifted toward the blue color due to a more significant contribution from the PFO emission. The EL color can be tuned between green (from the F8BT) and blue (from the PFO) shades by adjusting the polymer composition. The differences between the PL and EL band profiles were discussed.
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    Effect of PANI on Thermal, Mechanical and Electromagnetic Properties of HDPE/LLDPE/ PANI Composites
    (Univ Fed Sao Carlos, Dept Engenharia Materials, 2018) de Faria, Patrick Valadao [UNIFESP]; Backes, Eduardo Henrique; Montagna, Larissa Stieven [UNIFESP]; Pinto, Simone de Souza [UNIFESP]; Pessan, Luiz Antonio; Rezende, Mirabel Cerqueira [UNIFESP]; Passador, Fabio Roberto [UNIFESP]
    In this work, polyaniline (PANI) in emeraldine-base form, synthesized by chemical oxidation polymerization, was protonated with hydrochloric acid (HC1) Composites based on high-density polyethylene (HDPE) and linear-low density polyethylene (LLDPE) blends with PANI were prepared in molten condition using a torque rheometer The effect of compatibilizer agent (maleic anhydridegrafted high density polyethylene, HDPE-g-MA) and different contents of PANI on the blends-based composites was also investigated Thermal, mechanical, and electromagnetic (electric permittivity) measurements and morphological aspects of the composites were evaluated The addition of PANI content in the composites decreases the degree of crystallinity of HDPE and LLDPE blends, which implies that PANI particles make it difficult for co-crystallization to occur in the HDPE and LLDPE, respectively On the other hand, the addition of compatibilizer agent in the HDPE and LLDPE blends increased the degree of crystallinity The complex parameters of permittivity in the frequency range of 8.2 to 12.4 GHz vaned as a function of the PANI content m the blend It was also observed that the compatibilizer agent increased the composite stiffness and decreased the electric permittivity values This result shows that the increasmg rigidity of the molecular structure of the polyethylene matrix hindered the dissipation of the electromagnetic energy in the sample.