Síntese e caracterização de nanocompósitos constituídos por polianilina quitosana e dióxido de estanho

Abstract

The development of new polymeric materials with biodegradable, durable and inexpensive materials has been the subject of intense scientic research due to its innovative and promising applications in several fields. This dissertation aims to develop polymeric nanocomposites composed of polyaniline (PANI), chitosan (CS) and nanoparticles of tin dioxide (SnO 2 ), through a single synthesis route. For this, a systematic study of the synthesis route was carried out to obtain the final product. First, PANI/CS samples were prepared by modifying the percentage (m/V) of chitosan diluted in acetic acid and hydrochloric acid. At this stage, we evaluated the influence of the chitosan on the synthesis of polyaniline in the form of emeraldine salt, which is in a state of greater electrical conductivity. The results of the Fourier Transform Infrared Spectroscopy (FTIR) analysis of these samples indicated that all the composites where the chitosan was diluted in acetic acid had bands corresponding to PANI in the form of emeraldine salt with different degree of doping. The sample that presented the highest degree of doping was the sample synthesized with 0.5% m/V chitosan. Based on this result, this percentage of chitosan was used to synthesize nanocomposites. Second, polymeric nanocomposites consisting of PANI/CS/SnO2 and PANI/SnO 2 were prepared through a single synthesis process. The aniline polymerization was carried out in the presence of chitosan diluted in acetic acid, using dodecylbenzene sulfonic acid (DBSA) as protonating agent and ammonium persulfate (APS) as oxidizing agent. The tin dioxide nanoparticles, diluted in a solution of hydrochloric acid, were added during the synthesis process. SnO 2 nanoparticles were obtained by high energy milling using the chemically treated cassiterite, provided by the MELT Mining Industry, as raw material. By adopting cassiterite, we sought the possibility of reusing materials previously considered mineral waste. The structural characterization of the samples was carried out through X-ray diffraction (XRD); the thermal analysis was performed using differential scanning calorimetry (DSC) techniques, thermogravimetry (TGA) and differential (DTA); and spectroscopic analyses were executed through infrared (FTIR), photoelectrons excited by X-rays (XPS) and Mössbauer. The morphological characterization of the samples was carried out through scanning electron microscopy (SEM). The results indicated the formation of nanocomposites with different morphological characteristics and degrees of protonation.