Electrogravimetric analysis of poly(aniline-co-o-toluidine) copolymer films in the presence of fluoride ions

Polyaniline itself can be converted to its conductive form from its insulating form by applying an oxidising potential in which polyaniline is converted to its positive charge state. Anions in the target solution are driven into the positively charged polymer film by electrostatic force, and this process is reversed when a reduction potential is applied. Consequently, interfacial processes of polyaniline modified electrode make it viable to remove undesirable ions from the target solution. During this process, polyaniline operates as an ion-exchanger by directing specific ions at definite potentials, which is the principle of the electrochemically switched ion-exchange technique. Therefore, polyaniline can be employed as a convenient material to perform as a new ion-exchanger modified film in an acidic environment. On the other hand, an abrupt decrease in the electroactivity of polyaniline at elevated pH values restricts its use in such practical applications. To overcome this problem, copolymerization of aniline and o-toluidine is expedient as it will be able to enhance the electrochemical properties of polyaniline. Hence, several copolymers were synthesised in the presence of different aniline and o-toluidine feedstock ratios. It was found that the surface coverage value of a representative poly(aniline-co-o-toluidine) copolymer film was 139.7 nmol cm−2 compared with 76 nmol cm−2 for pure Pani under identical conditions. In addition, the redox cycling in monomer-free NaF solutions showed that the poly(aniline-co-o-toluidine) film exhibited excellent reversibility between redox reactions at pH 6.60. These outcomes clearly illustrate the contribution of o-toluidine to the electrochemical properties of polyaniline at raised pH medium.