Structural reorganization of the PPy/DBS films caused by the reduction branch of potentiodynamic polymerization

Polypyrrole/dodecylbenzenesulfonate (PPy/DBS) films were synthesized in aqueous solution by cyclic voltammetry. The polymerization carried out at slow scan rates produces two cathodic peaks on the reduction branch. A single reduction peak was obtained at scan rates higher than 50 mV s−1. Two different polymeric structures have been proposed to explain the observed cathodic splitting. Structure I was associated with the organization reached by slow rate electropolymerization processes. Structure II was obtained when I was permanently modified by electrochemical reduction. Under electrogeneration by potential cycling a constant amount of I is generated on every cycle, providing a constant reduction peak A charge. However, the charge involved in peak B, where structure II is reduced, increases with the cycling. Structure I has a lower energetic content than structure II: it is reduced at lesser cathodic potentials than II. Voltammetric and EDX measurements indicated that a main cationic transport occurred during the redox process of the PPy/DBS. However, a certain amount of Na+ cations was not interchanged, since they were stabilized inside the polymer, forming ion pairs with an extra quantity of DBS− anions trapped in the polymer matrix during the polymerization process.