Estudo estrutural e morfológico de nanocompósitos formados por polipirrol e óxidos metálicos

Abstract

In this work were synthesized the Polypyrrole (PPy), PPy/ -Al2O3 and PPy/CeO2 nanocomposites via conventional chemical synthesis using ammonium persulfate (APS). The samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC) and DC Conductivity Measurements. The XRD profile of the polymer showed that it is a semicrystalline structure with aproximately 17 ( 3)% of crystallinity. Through the Le Bail method was possible to identify that the synthesized polymer had dimeric structure and that it is cell unit is composed of only one dimeric molecule. The nanocomposites profiles showed that the concentration of metal oxides used in the synthesis favored the metal phase, but it was still possible to visualize the polymer contribution, showing that the structure of the two phases coexist in the form of a nanocomposite. The morphology of the samples was evaluated via SEM, evidencing cauliflower morphology of the polymer, which consists of incomplete spheres that form a cluster of nanoparticles. The nanocomposites showed core-shell morphology, and it can be observed that the polymer covered the particles of the metallic oxides through a thin polymer layer. SEM images also allowed the identification of phases and matrices in nanocomposites. The thermal measurements via DSC allowed to verify the hidrophobic character of the inorganic phase, promoting the repulsion of water molecules of internal hydration of the polymer. This fact caused the initial decomposition temperature of the nanocomposites to become smaller. Corroborating with these DSC data, it was observed that the electrical conductivity of the polymer is lower than of the nanocomposites. This fact can be interpreted in relation to the presence of hydratation water in PPy. The nanocomposites presented 80% higher electrical conductivity when compared to the pure polymer. Thus, the goals of this work to carry out a structural and morphological study of PPy, PPy/ -Al2O3 and PPy/CeO2 nanocomposites and the correlation of these results with the values of DC electrical conductivity