Comportamento espectro-eletroquímico de filmes finos de polianilina: estratégias para aplicações tecnológicas

Abstract

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. This study investigates the influence of electropolymerization regimes on the properties of PANI thin films synthesized via galvanostatic (PANI-G), potentiodynamic (PANI-V) and electrochemically converted film (PANI-C). 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. Ex situ structural, morphological, and chemical aspects of the PANI films were 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-G film was uniformly deposited. In contrast, PANI-V film displayed a non-uniform rough surface with granular structures, indicating a morphology with disorderly manner. Through cyclic voltammograms, in 0.5 mol L-1 H2SO4 between -0.2 to +0.9 V vs. Ag/AgCl/KCl (3M), PANI-G film 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. The converted film, PANI-C, appeared to have transitional features from both films. Rotating disk voltammetry was employed to measure the permeability of the films. Both PANI-G and PANI-C films exhibited similar values, 2.34 × 10⁻² and 2.03 × 10⁻² cm·s⁻¹, respectively, whereas PANI-V displayed a lower permeability of 9.72 × 10⁻³ cm·s⁻¹. Potentiometric measurements were carried out employing the Open Circuit Potential (OCP) method. PANI-G and PANI-V exhibited super-Nernstian responses of -73.4 mV·pH⁻¹ and -79.9 mV·pH⁻¹, respectively, within the pH range 2–6, while PANI-C showed a near-Nernstian response of -53.8 mV·pH⁻¹ over pH 2–10. The findings indicated that the electropolymerization regime significantly affects the film’s structure, electrochemical behavior, and sensing performance, supporting the rational design of PANI-based materials, likely due to the conformational factor of the polymer chains, leading to the most appropriate choice of surface depending on the desired application.