Electrochemical synthesis of polyaniline-polypyrrole composite coatings oncarbon fibres in aqueous toluene sulphonate solution

Polyaniline and polypyrrole were codeposited electrochemically on carbon fi bres under potentiostatic conditions. Electropolymerisation was carried out by varying the applied potential and the feed ratio of monomers. The progr ess of electropolymerisation was monitored by weight gain analysis and infr ared spectroscopy. The thermal stability of the coatings was determined by using thermogravimetric analysis and differential scanning calorimetry. Cha racteristic behaviour of polyaniline and polypyrrole can be deduced from th e weight gain plots. Formation of polyaniline-polypyrrole composite coating s was further confirmed by the presence of characteristic peaks for polyani line and polypyrrole in the infrared spectra. Thermal analysis also reveale d the behaviour of the composite. Composite coatings composed of polyanilin e and polypyrrole were formed at applied potentials of <1.0 V. Polypyrrole is preferentially formed at 1.5 V. Scanning electron micrographs were also used to illustrate the composite behaviour.