Spectroelectrochemical study of a soluble derivative of poly(aniline) in a room temperature ionic liquid

Poly(phenylene sulfide phenyleneamine), PPSA, is a soluble copolymer of poly(aniline) and poly(phenylene sulfide). Its electrochemical behavior has already been studied in both aqueous and organic media in the presence of different electrolytes, where it was observed the loss of electroactivity after few cycles. In this paper, the spectroelectrochemical characterization of PPSA films in a room temperature ionic liquid (RTIL), 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanes sulfonyl)imide (BMMITFSI), is shown. The electrochemical response of a PPSA modified electrode in BMMITFSI is different from that obtained in organic solvent/salt systems. In RTIL, two reversible redox processes were observed and they were assigned to the reversible radical cation/dication transition based on “in situ” UV–vis and Raman spectroscopic studies. The stabilization of the dicationic species in RTIL is an explanation for the reversible electrochemical response of the PPSA in BMMITFSI; on the contrary, when the electrochemical oxidation is carried out in conventional organic electrolytes, once the oxidation of the sulfur atom occurs, a loss of electroactivity is observed being not possible to recover the pristine state of the polymer. FTIR and XRD data obtained for the fully oxidized polymer in acetonitrile are consistent with the formation of a networked polymer due to the electrophilic attack of the positive sulfur atom on the activated aromatic rings. It is not the case in RTIL due to the shielding of the charged sulfur atoms avoiding its reaction to other chains to form the networked polymeric matrix.