Electrodeposition and characterisation of copolymers based on pyrrole and 3,4-ethylenedioxythiophene in BMIM BF₄ using a microcell configuration

Electrochemical copolymerization of pyrrole (Py) and 3,4- ethylenedioxythiophene (EDOT) was performed in an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, (BMIM BF4) employing a 'micro-cell' in order to use the materials efficiently. Characterization of the copolymers formed on an ITO substrate was performed for different Py: EDOT ratios (1:2, 1:1, 2:1) in both aqueous and ionic liquid electrolytes. The three copolymers displayed different absorbance spectra with λmax of the polaron species at 507, 540 and 580 nm for PPy-co-PEDOT ratios of 1:2, 1:1, 2:1, respectively. Electrochemical and spectroelectrochemical analysis revealed that the properties of the copolymer depend upon the Py/EDOT monomer ratio used. The copolymer PPy-co-PEDOT (2:1) displayed good stability, a switching time of 20 s and a colouration efficiency of 101.3 C-1cm2. The presence of Py in the copolymer stabilised the polaron state of the copolymer and allowed greater ion mobility compared to the PEDOT alone.