JAQUELINE DE SOUZA DA SILVA
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Artigo IPEN-doc 27193 SAXS signature of the lamellar ordering of ionic domains of perfluorinated sulfonic-acid ionomers by electric and magnetic field-assisted casting2020 - SILVA, JAQUELINE S. da; CARVALHO, SABRINA G.M.; SILVA, RODRIGO P. da; TAVARES, ANA C.; SCHADE, ULRICH; PUSKAR, LJILJANA; FONSECA, FABIO C.; MATOS, BRUNO R.At present, small angle X-ray scattering (SAXS) studies of perfluorinated sulfonic-acid ionomers (PFSAs) are unable to fully determine the true shape of their building blocks, as recent SAXS modelling predicts disk- and rod-like nanoionic domains as being equally possible. This scenario requires evidence-based findings to unravel the real shape of PFSA building blocks. Herein, a SAXS pattern signature for a lamellar nanophase separation of the ionic domains of Nafion is presented, backed by mid and far infrared spectroscopy (MIR and FIR) and wide angle X-ray scattering (WAXS) data of Nafion in different ionic forms, a broad range of ionic phase contents (EW ~ 859–42 252 g eq-1) and temperatures. The study indicates that the lamellar arrangement of the ionic domains is the most representative morphology that accounts for the physical properties of this ionomer. The lamellar SAXS reflections of Nafion are enhanced in electric and magnetic field-aligned membranes, as confirmed by atomic force microscopy (AFM). Electric and magnetic field-assisted casting of Nafion allowed producing nanostructured and anisotropic films with the lamellas stacked perpendicularly to the field vector, which is the direction of interest for several applications. Such nanostructured Nafion membranes are bestowed with advanced optical and proton transport properties, making them promising materials for solar and fuel cells.Artigo IPEN-doc 23078 Proton and cesium conductivity in perfluorosulfonate ionomers at low and high relative humidity2017 - MATOS, BRUNO R.; SILVA, JAQUELINE S. da; SANTIAGO, ELISABETH I.; PARRA, DUCLERC F.; CARASTAN, DANILO J.; FLORIO, DANIEL Z. de; ANDRADA, HEBER E.; CARRERAS, ALEJO C.; FONSECA, FABIO C.Nafion exhibits one of the highest proton conductivity at room temperature and it is the standard electrolyte of proton exchange membrane fuel cells (PEMFC). However, the temperature dependence of ionic conductivity of Nation is highly dependent on the measuring conditions and it is still a matter of debate. In the present study, detailed dielectric spectroscopy (DS) measurements in both dry (under N2 flow) and water-saturated conditions were carried out in a broad range of temperature and frequency. Such DS results were correlated to differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) data taken in similar conditions. The main results revealed that in samples conditioned in N2 flow (RH ~0%) the transport of both proton and cesiumions is coordinated with the dynamics of Nafion relaxations. In hydrated Nafion (proton form), conductivity measurements at different frequencies revealed two regimes: one at high-frequency, in which the Vogel-Tamman- Fulcher (VTF) law indicates a close relation between the polymer glass transition temperature Tg; and, a second one at low frequency, bearing great similarity to the transport observed in nearly dry samples. The reported experimental results contribute to disentangle the intricate transport properties of Nafion.