Abstract

A set of nine monomers derived from diaryl-cyanovinylene, -carboxyvinylene and -cyanobutadiene were synthesized as were the corresponding polymers resulting from the chemical polymerization of the monomers in the presence of an almost quantitative amount of FeCl₃ in chloroform. The aim of this work was to investigate the effect of the chemical structure of the polymers on their charge capacitance and stability upon galvanostatic charge/discharge cycling. The electrochemical performances of composite electrodes based on polymer, acetylene black and PTFE have been investigated in acetonitrile containing 1 M Et₄NBF₄ using cyclic voltammetry and galvanostatic charge/discharge cycling experiments. The best performances in terms of charge capacitance for both the p- and n-doping processes were demonstrated with poly(7) (2E,4E)-2,5-di-2-thienylpenta-2,4-dienenitrile and poly(9) (2E)-3-(2,2′-bithienyl-5-yl)-2-(2-thienyl)prop-2-enenitrile since values as high as 245 C g⁻¹ were obtained with poly(7) in its n-doped state and 325 C g⁻¹ with p-doped poly(9). The energy density (68 Wh kg⁻¹) and power density (24 kW kg⁻¹) delivered by a poly(9) capacitor are in good agreement with those expected from cyclic voltammetry and galvanostatic charge/discharge experiments performed with single electrodes. Unfortunately, a capacitance loss was observed upon cycling and was ascribed exclusively to the n-doping process occurring at the negative electrode since the capacitance of the positive electrode remained almost unchanged during these experiments.