An approach to the electrochemical activity of poly-(phenothiazines) by complementary electrochemical impedance spectroscopy and Vis–NIR spectroscopy

The electroactivity of two poly-(phenothiazine), the poly-(Azure A) and the poly-(Methylene Blue), has been compared in this work. The spectroelectrochemical results prove clearly the existence of two electroactive moieties integrated in the polymeric lattice, the phenothiazine ring (detected by changes of absorbance at 590 and 685 nm) and the newly formed covalent links which fixes the monomers in the backbone of the polymer (detected by changes of absorbance at 460 and 875 nm). Differences in the electrochemical response of both polymers are due to differences in this covalent link. However in both polymers, the charge balance during electrochemical reactions takes place by the exchange of one anion species and one cation species during the double electronic transference in both types of electroactive centers. Electrochemical impedance analysis together with the spectroelectrochemical (cyclic voltammetry + Vis-Near IR spectroscopy) makes possible to throw light on the mechanistic model of the electrochemical reaction of these polymers taking into account the coupled electronic/ionic transports, the trapped polarons (pinning model), structural configurations and inner water molecules.