Electrodes modified by sulphonated Poly (Aryl Ether Sulphone) (S-PES) for electroanalytical applications

The use of polymeric materials for electrodes modification, with the aim of increasing the affinity for the analyte, increasing sensitivity, lowering the limits of detection and minimizing or completely avoiding interferences is becoming an interesting challenge in recent electroanalytical methods. Although scarcely characterized or appropriately designed for the modification of electrodes, thanks to its large use in fuel cell devices, Nafion® is one of the most popular polymer also in electroanalytical applications [1]. Poly (Aryl Ether Sulphones), commonly called PES, are well-known engineered thermoplastic materials [2], with excellent properties thanks to their aromatic skeleton and charged groups, such as thermal and mechanical strength, resistance to oxidation and acid catalyzed hydrolysis. Moreover, they present high glass transition temperature, good solubility in polar aprotic and halogenated solvents, radiation stability, low flammability and toughness, together with low costs. In this context, sulphonated Poly (Aryl Ether Sulphone) (S-PES) was studied as a new material for the production of modified electrodes in comparison with Nafion®. The modified electrodes are fully characterized by cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS). Different parameters have been studied: the quantity and the form (acidic, salt, linear, branched,...) of the polymer, different IECs, its method of drying, the casting solvent, its stability in air or solution. In particular, as the Figure shows, 1 % linear PES in the acidic form, dried at 25 °C in a oven, after deposition from a N-Methylpyrrolidone solution, appears to present the best performances in terms of higher voltammetric peak currents, more stability and less resistive behaviour, superior to Nafion®, maintaining the partial electrochemical and chemical reversibility and the diffusive control. [1] V. Pifferi, V. Marona, M. Longhi, L. Falciola, Electrochimica Acta, 109, (2013), 447-453. [2] R.T.S. Muthu Lakshmi, J. Meier-Haack, K. Schlenstedt, H. Komber, V. Choudhary and I.K. Varma, Reactive and Functional Polymers, 66 (6), (2006), 634–644.