Study on pH-Response of Polyaniline Film by Zero-current Potentiometry

An electrochemically polymerized polyaniline film modified pencil graphite electrode was connected with the novel electrochemical testing system, and its pH-response was studied by the zero-current potentiometry. As shown by the experimental results, the polyaniline prepared was present mainly as the intermediate oxidative form of emeraldine. The protonation and de-protonation of polyaniline were dependent on pH-values of the B-R buffer medium, and linear relationships between values of Ezcp and pH were obtained in 2 sections in the ranges of pH 1.81-5.43 and pH 5.43-9.91, having the intersection at pH 5.43. The apparent pKa value of emeraldine was found to be 5.43 as calculated from the pH value.