Synthesis of conducting azopolymers by electrochemical grafting of a diazonium salt at polypyrrole electrodes

• A new strategy for obtaining polypyrrole with pendant azobenzene moieties is proposed.
• Polymer functionalization was done by electrochemical reduction of a diazonium salt.
• Grafting of 4′-nitroazobenzene was evaluated by cyclic voltammetry and spectroscopy.
• Nonlinear optical response of functionalized polypyrrole has been investigated.
• All investigations confirmed the grafting of chromophore groups at polypyrrole films.

In this paper we report a new strategy for obtaining conducting azopolymers having pendant azobenzene moieties via functionalization of polypyrrole by electrochemical reduction of 4-[(4′-nitrophenyl)azo]benzenediazonium tetrafluoroborate (NABDBF4−). The functionalization of polypyrrole films with 4′-nitroazobenzene (NAB) groups has been evaluated by cyclic voltammetry and by spectroscopic techniques such as XPS, Raman and UV–vis spectroscopy. Moreover, the third-order nonlinear optical response of NAB-functionalized polypyrrole has been investigated using the optical third-harmonic generation technique. All these investigations confirmed the presence at the polymeric films surface of the functional groups introduced by the electrochemical reduction of diazonium salt. The versatility of this methodology allows not only the functionalization of polypyrrole-type materials with chromophore groups, but can also be successfully applied to other conjugated polymer systems in order to create various photoresponsive materials.

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