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)
Résumé
A new transfer model is proposed to explain ac-electrogravimetry response of p-doped
films. This model
takes into account the exclusion effect occurring as a result of the anion transfer. The insertion/expulsion
of anions inside a
film involves simultaneously the expulsion/insertion of free solvent molecules. The
number of solvent molecules excluded depends on the volume of anion transferred. Solvent transfer
stimulated by the conformational changes of
films constitutes the remaining electrogravimetric response
when the exclusion process cannot explain by itself this response. Consequently, the kinetics of this free
solvent transfer can be directly related to the kinetics of conformational changes. This model was
validated in poly(o-toluidine) thin
films where electrochemical kinetics were quantitatively investigated
as a function of the applied potential. As far as we know, for the
first time, charge transfer and
conformational changes could be kinetically separated. This new transfer model may respond to
fundamental questions on the electrochemistry of conducting polymers, which may have a significant
impact on a large number of applications.
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