Effects of anion size on the electrochemical behavior of H2SO4-structured poly(o-toluidine) films. An ac-electrogravimetry study in acid solutions

Abstract

ac-Electrogravimetry has allowed an easy separation of kinetic information to be evaluated for all the transferred species in three different H2SO4-structured poly(o-toluidine) or POT films, POT-NO3−, POT-ClO4− and POT-Cl− films when they are polarized between the pernigraniline (oxidized) and leucoemeraldine (reduced) forms. It is clear that larger anions slow down the electrochemical transitions of POT films, but the effects of anion transfer on hydrated protons and free solvent transfers are affected. For the same polymeric structure of a POT film, the kinetics of all specie transfers have been evaluated considering the size of species, geometric molecular structure, the interactions with the polymer structure of POT, the hydrophobicity of species transferred, the polymeric rearrangements and the oxidation state of the film. When the polymeric structure is not adapted to the anion in solution, the transfer of non-charged molecules has a mixed kinetic control depending on anion transfer and mechanical contractions/expansions of film. By taking into account all these considerations, the versatility of one type of sensor device could be improved and extended to different analytical situations.