Caracterização dos processos eletroquímicos em filmes automontados de poli(o-metoxianilina) e poli(ácido-3-tiofeno acético).
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Data
2003-05-19Autor
Strixino, Francisco Trivinho
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In this work, the electrochemical characterization of a self-assembled
film containing two conductive polymers, poly(o-methoxyanilina)(POMA) and poly(3-
thiophene acetic acid)(PTAA), is presented. The technique that allows to obtain
these films is known as layer-by-layer (LBL) deposition. It consists in a spontaneous
adsorption of species with opposite charges. The technique used for the
electrochemical characterization was cyclic voltammetry coupled with mass variation
using an electrochemical quartz crystal microbalance (EQCM), which allows the
characterization of the LBL film mass/charge transport during the redox process.
Electroacoustic impedance experiments of the LBL films with different number of
bilayers show that the viscoelastic and mechanic tension properties do not change
significantly in the potential range studied. Therefore, allowing the use of the
Sauerbrey equation for converting the frequency values in mass values. The charge
compensation mechanism was determined using the species flux (ions+solvent
molecules) compared with POMA those casting films. The POMA-PTAA LBL film
presents a charge compensation mechanism due to simultaneous intercalation of
cations and anions. This behavior suggests the existence of a pseudo-self-doping
mechanism related to carboxilic lateral groups interactions through the alternating
layers structure of POMA-PTAA. The charge in the deprotonated carboxilic groups
neutralize the charge generation of the imina groups present in the POMA backbone,
which gives a decrease of the total mass change of the film. In this sense, the LBL
technique could be an alternative method to prepare conducting polymer films
modifying their electrochemistry properties.