Polyviologen synthesis by self-assembly assisted grafting

Abstract

In this work a new method for electrochemical polymerization of a viologen derivative is presented. A precursor, having an isothiocyanate group as a “head”-group and a cyanopyridine group as a “tail”-group (SCNCP), suitable for self-assembly was designed and synthesized. An adsorbed layer of SCNCP was achieved by assembling isothiocyanate “head”-groups onto gold electrodes or onto gold with an amino-terminated monolayer of cysteamine (SNH₂). The purpose of the cyanopyridine “tail”-group is to act as a hook and linker to cyanopyridine based monomers. In this work dimerization between two cyanopyridines, the “tail”-group and a synthesized linear cyanopyridine monomer (LCP), were induced by electrochemical reduction. The SAMs and films were characterized by electrochemical and spectroscopic techniques (UV-vis and FTIR), and show characteristc FTIR spectra and electrochemical redox responses of viologens. AFM and SEM images show wires extending out from the electrode substrate when viologen films were formed on SNH₂–SCNCP modified gold surfaces. The new viologen derivative not only broadens the field of applications of viologens in various electronics, but also enables structural regularity and formation at different surfaces.