Poly(3,4-Ethylenedioxythiophene) (PEDOT) polymers doped with Sulphonated Polyarylethersulphones for electroanalytical applications

Among Polythiophene derivates, Poly(3,4-Ethylenedioxythiophene) (PEDOT) is one of the most successful conducting polymer due to its excellent environmental stability and high electrical conductivity. Numerous researches have been conducted on PEDOT synthesis by electrochemical and chemical polymerization of 3,4-Ethylenedioxythiophene (EDOT). Chemical approaches, performed by high-concentration water-based emulsion polymerization of EDOT, produce PEDOT precipitates as dark-blue powders, which are insoluble in water [1]. To improve PEDOT solubility and conductive properties, PEDOT polymers can be doped with sulphonated dopants, the most commonly used being 2-Naphthalenesulphonic acid and para-toluene sulphonic acid, which however yield to scarce possibility to modify and tailor the properties of the final materials. Anyway, as already shown in previous investigations, electrodes modified with SPAES (e.g. deposited on glassy carbon supports) demonstrated to possess good electrochemical performances in terms of higher analyte currents, strongly dependent from the casting solvent [2] and on the ion exchange capacity (IEC). In this context, in the present work, Sulphonated Polyarylethersulphone (SPAES) polymer, synthesized via homogeneous synthesis with different IEC [3], is proposed as new doping agent, allowing both a tight control over the IEC and a charge separation already present in SPAES structure, deriving from the pre-sulphonated comonomer [3,4]. PEDOT doped with SPAES is synthesized via a high-concentration solvent-based emulsion polymerization of EDOT in four different reaction solvents (N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone). Bare SPAES, bare PEDOT and PEDOT doped with 2-Naphthalenesulfonic acid are also synthesized for comparison. Despite the very low amount of SPAES used (1% w/w respect to EDOT), PEDOT_SPAES appears to be a material very different from its original components. For instance, wide-angle scattering (WAXS) measurements show how the crystalline structure of bare PEDOT or PEDOT doped with 2-Naphthalenesulfonic acid is lost, with an increase of the amorphous phase when SPAES is added as doping agent. These new materials, when used as electrode modifiers, yield to an increase in the general electroanalytical performances, in terms of higher peak currents (with respect to the Ru probe). In particular, the type of casting solvent appears to be an important parameter for the modulation of the adhesion, homogeneity and porosity of the polymeric membrane on the electrode surface and consequently of the electrochemical signal. The electrochemical investigation demonstrates also the importance of other variables, such as IEC, stabilization time, drying temperature and pressure, to assure a good electrode response. Therefore, a Principal Component chemometric Analysis is also employed for results rationalization. References [1] Y. Lei, H. Oohata, S. Kuroda, S. Sasaki and T. Yamamoto, Synth. Met. 149 (2005) 211-217. [2] L. Falciola, S. Checchia, V. Pifferi, H. Farina, M.A. Ortenzi, V. Sabatini, Electrochim. Acta 194 (2016) 405-412. [3] V. Sabatini, S. Checchia, H. Farina, M. A. Ortenzi, Macromol. Res. 483 (2016) 285-291. [4] V. Sabatini, H. Farina, M. A. Ortenzi, Polym. Eng. Sci. 57 (2017) 491-501.