Reactive polymer films: Polypyrrole oxidation kinetics in aqueous solution

The oxidation kinetics of electrogenerated polypyrrole films was studied in aqueous solution. The influence of reactant concentrations (LiClO4 in solution and active centres in the polymer film) and temperature on the kinetics has been studied. The usual procedure for any kinetic study was now repeated for different initial states, attained by electrochemical reduction at the same cathodic potential for different reduction times. For rising reduction times, lower kinetic coefficient (k) and higher activation energies (Ea) were obtained. The activation energy is assumed to include rising conformational energy for more packed conformations of the initial states. Both kinetic magnitudes become a way to quantify the initial packing conformational degree. So, kinetic magnitudes can include structural information opening a new window for the chemical kinetics of reactive macromolecules that could be extended to reactive biopolymers. When compared the evolutions of k and Ea experimental changes from aqueous and acetonitrile solutions of the same salt, important differences were found. Evolutions of k and Ea from different solvents could be used as tools to quantify the polymer–solvent interaction evolution along the reaction.