Macroscopic modulation of the π-electron density of pendant groups grafted on conductive polymers

The influence of the redox switching reaction of a conductive polymer upon the π electron density of grafted pendant groups has been studied. Poly(N-phenylpyrrole) and poly(N-benzylpyrrole) have been compared by means of IR spectroscopy and molecular modelling. In the case of poly(N-phenylpyrrole), the evolution of the infrared vibrational bands expresses a reversible modulation of the π electron density of the benzene nucleus when the polymer is switched from its reduced to its oxidized form. There is no such effect when the aromatic moieties are separated from the polymer backbone by a CH2 group. Moreover, molecular modelling suggests that oxidation of poly(N-phenylpyrrole) makes it possible to break the conjugation between the benzene nuclei and the polypyrrole backbone.