Síntese e caracterização do nanocompósito formado por polipirrol e óxido de grafeno

Abstract

In this work, Polypyrrole (PPy), Graphene Oxide (GO), PPy/GO C and PPy/GO I nanocomposites were synthesized via conventional and interfacial chemical synthesis in the presence of ammonium persulfate (APS) and sulfuric acid (H2SO4). The samples were characterized by UV-Vis Spectroscopy, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and AC Electrical Conductivity Measurements by Impedance Spectroscopy. By means of UV-Vis spectra it was possible to verify and confirm the polymerization of polypyrrole, graphene oxide and nanocomposites when inserted GO in synthesis together with PPy. The XRD profiles of the polymers showed that it is a semi-crystalline structure with approximately 30 and 29 (±3)% fractional crystallinity for PPy-C and PPy-I, respectively. The nanocomposite profiles showed that the concentration of graphene oxide used in the synthesis favors the polymer phase, but it is still possible to visualize the contribution of the GO, showing that the structures of the two phases coexist in the form of nanocomposites, evidencing that basically no crystalline order was introduced into the structure of nanocomposites. The crystallinity percentage for the nanocomposites presented crystalline fraction of 24 and 42 (±3)% for PPy/GO C and PPy/GO I, respectively. The morphology of the samples was evaluated by SEM, evidencing the cauliflower morphology of PPy, which consists of complete and incomplete nanosphere microspheres of diverse sizes that form a cluster of nanoparticles. SEM micrographs confirmed the lamellar morphology for the GO, where it is formed by a finite layer, which has a nanometric thickness. The nanocomposites presented morphology of the core-shell type, and it can be observed that the polymer covered the oxide particles through a thin polymer layer. SEM images also allowed the identification of phases and matrices in nanocomposites. The FT-IR analysis allowed to identify and assign the characteristic bands for the study materials, showing that π-π stacking occurs between PPy and GO when in nanocomposite. Through the electrical conductivity it was possible to verify that the PPy-C had an improvement in its conductivity with the GO insertion. However the PPy-I synthesized resulted in better electrical conductivity, which is not overcome by the nanocomposites, since the synthesis method results in a more oriented polymerization.