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Development of ion jelly thin films for electrochemical devices
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Resumo(s)
Ionic liquids (ILs) are promising materials which have been used in a wide range of applications. However, their major limitation is their physical state. In order to address this challenge, a self-supported IL-based material was developed by combining gelatine with an IL, originating a quasi-solid material named Ion Jelly (IJ). This is a light flexible material, dimensionally stable, with promising properties to develop safe and highly conductive electrolytes. This thesis is focused on the characterization of IJ films based on different ILs. The conductive mechanisms of IJ materials were studied using dielectric relaxation spectroscopy (DRS) in the frequency range 10-1−106 Hz. The study was complemented by differential scanning calorimetry (DSC) and pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy.
A glass transition was detected by DSC for all materials allowing to classify them as glass formers. From dielectric measurements, transport properties such as mobility and diffusion coefficients were extracted. Moreover, it was found that the diffusion coefficients and mobility are similar for the IL and IJ, especially for the IL EMIMDCA.
Since for BMIMDCA, those properties significantly change upon hydration, the influence of water content [0.4 - 30% (w/w)] was also studied for the ILs. In particular for BMPyrDCA with 30% water, it was analyzed the reorientational polarization by the complex permittivity and electric modulus, from which three different processes were identified: a secondary relaxation with Arrhenian temperature dependence, the process that is believed to be behind the dynamic glass transition and the mobility of charge carriers.
An application of the IJs was successfully explored with a chemoresistive gas sensor made up by different IJs as active layer, which is an electronic nose formed by an array of such sensors. The performance of this e-nose revealed its ability to correctly detect eight common volatile solvents.
Descrição
Dissertação para obtenção do Grau de Doutor em Química Sustentável
Palavras-chave
Ionic liquids Ion jelly Dielectric relaxation spectroscopy Differential scanning calorimetry PFG – nuclear magnetic resonance