Banca de QUALIFICAÇÃO: LEONARDO GOMES MEDEIROS

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : LEONARDO GOMES MEDEIROS
DATE: 30/04/2025
TIME: 10:00
LOCAL: videoconferência
TITLE:

Spectroelectrochemical behavior of polyaniline thin films: synthesis and characterization.

KEY WORDS:

Polyaniline; thin films; electropolymerization; 3D printing; SEC cell; spectroelectrochemistry

PAGES: 60
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Analítica
SPECIALTY: Eletroanalítica
SUMMARY:

The comprehensive understanding of dynamic interfacial processes and their implications in the conductive materials synthesis enables its use in important technological applications. Polyaniline (PANI), a conductive conjugated polymer, has a unique structure that allows it to be used in various applications; including, electronic devices, corrosion protection and sensor development. However, its distinctive features are result of how the material is synthesized and/or treated. Thus, the aim of this study was to investigate the correlation across the properties of PANI thin films obtained via galvanostatic (PANI-G) and potentiodynamic (PANI-V) electropolymerization. Electrochemical studies of the synthesized materials confirmed the redox behavior and favorable electrochemical performances of the films. The ex situ structural, morphological, and chemical aspects of the PANI films were further analyzed using Raman, Scanning Electron Microscopy (SEM) and Dispersive X-ray Spectroscopy (EDS). Through SEM analysis, galvanostatic electropolymerization exhibited a smooth and homogeneous surface, in which the PANI film was uniformly deposited. In contrast, the PANI-V film displayed a non-uniform rough surface with granular structures, aspects that indicates a morphology with disorderly manner. Additionally, the cyclic voltammograms of PANI-G films in 0.5 mol L-1 H2SO4 between -0.2 to +0.9 V vs. Ag/AgCl/KCl (3M) exhibited a higher energy need for interconversion processes at the first voltammetric cycle, indicating greater chain organization and higher resistance to proton transport during electrochemically induced interconversion processes. Moreover, it was observed a tendency of voltammetric profile peaks of PANI-G leaning to a similar behavior as described for PANI-V as successive cycles occurred, which led to a third and possible form, PANI-C film. Furthermore, 3D-printed spectroeletrochemical (SEC) cells were employed to couple UV-Vis, Raman and electrochemical techniques for in situ real-time measurements during synthesis of PANI-G. The Raman spectra indicated that, during synthesis, PANI-G film displayed a lower protonation and oxidation degree when compared to the end of polymerization, as the emeraldine salt was formed. The converted film, PANI-C, appeared to have transitional features from both films. Hence, the electrochemical characteristics of the synthetized PANI films differed accordingly to the synthesis method, which can be attributed to the conformational factor of the polymer chains leading to the most appropriate choice of surface depending on the desired application.

COMMITTEE MEMBERS:
Interno - 1645110 - CARLOS ALBERTO MARTINEZ HUITLE
Externo à Instituição - GABRIEL NEGRÃO MELONI - USP
Externo ao Programa - 1199268 - JAILSON VIEIRA DE MELO - nullPresidente - 2413537 - POLLYANA SOUZA CASTRO