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 H 2 SO 4 -structured poly(otoluidine) or POT films, POT-NO 3 -, POT-ClO 4 and POT-Clfilms 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.

Electrochemically induced free solvent transfer in thin poly(3,4-ethylenedioxythiophene) films

“…Lateral interactions between randomly distributed electroactive sites lessen the theoretical value of considering the Laviron model based on the Frumkin-type isotherm [29]. These low values point to a very intensive lateral interaction between charged sites of PEDOT.…”

“…Extrapolating to PEDOT, it is possible to estimate and considering that surface concentration of is equal to surface concentration of and , [28,29]. Thus, Table 1 shows the evolution of the number of on the oxidation state of PEDOT.…”

“…Electrochemical impedance analysis proves useful to separate temporally different ions/charge transfer, however, this technique is blind for non-charged species transfer [26]. Combining electrochemical and mass impedance spectroscopy, ac-electrogravimetry, allows an objective separation between ions/charge and solvent transfer [27][28][29].…”

“…However, molecular reconfiguration is assumed in the electrochemical mechanisms of conducting polymers [46]. An approximation to polymer conformational movements consists of solving the stoichiometric relation between the doping molecules, in this case , and the solvent transfer [28,29]. By using the commercial software ChemBio3D Ultra v. 12.0 ChemBioOffice 2010, the volume of …”

Polymer dynamics in thin p-type conducting films investigated by ac-electrogravimetry. Kinetics aspects on anion exclusion, free solvent transfer, and conformational changes in poly(o-toluidine)

“…As an example, this control can take place in films where slower electronic transfer along dynamic chains introduces a slow conformational change with slow noncharged species transfer. However, under specific experimental conditions or for very thin films, the transfer of neutral solvent can be kinetically controlled (although "indirectly") because both insertion/expulsion of ions and movements of polymeric backbones (both kinetically controlled) have a "direct" effect on the solvent transfer [16,17]. In the view of that, the transfer of neutral solvent, or in other words, the hydration extent of ICPs could be modulated varying the oxidation state via an external potential.…”