CONICET | Buscador de Institutos y Recursos Humanos

The copolymerization of m-chloroaniline (mClA) and aniline (Ani) in variable ratios was performed by galvanostatic oxidation in 1 M HCl medium. The polymerization was carried out on glass plates covered by a fluorine-doped tin oxide (FTO) conductive layer, yielding thin polymer films. The resulting polymers were characterized by UV-Vis and fluorescence emission spectroscopy at different electrode potentials between 0.1 and 0.8 V in the standard hydrogen electrode scale (SHE). The UV-Vis spectra were recorded between 300 and 600 nm. A bilinear decomposition of these spectra at 0.1 V (SHE) allowed to obtain the mole fractions of each monomer in the polymer films as a function of the feed solution composition. These values were interpreted in terms of the terminal copolymerization model (TCM) through the Mayo-Lewis equation. The f1 and F1 values were satisfactorily fitted, the results indicating higher reactivity for mClA. The fluorescence spectra show a low emission in the reduced form which is quenched at higher potentials, when PAni is oxidized and becomes conductive. The maximum attenuation at the anodic limit is observed for PAni (F1 = 0), and a steep decrease is observed at low F1 values. A second steep change appears between F1 = 0.45 and 0.55. To investigate that, Monte Carlo simulations of the TCM were performed to obtain the average monomer distributions in the chain. It is found that at F1 = 0.45 about 5 % of Ani units form blocks of three units (with much lower contents of longer Ani blocks), but at F1 = 0.55 only 0.5 % of 3 consecutive Ani units is found. As three consecutive aniline units are needed to allow the formation of a quinone imine, the absence of fluorescence attenuation for F1 > 0.6 V is attributed to the absence of quinone imine units in the oxidized polymer.

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