The adsorption of viologen-containing polyelectrolytes on the surface of carboxylate-terminated, self-assembled monolayers was investigated by voltammetric methods. The two polyelectrolytes used had either butyl (VC4) or undecyl (VC11) linkages between the repeating viologen (4,4′-bipyridinium) subunits. Both polyelectrolytes were found to adsorb at nuetral pH on monolayers prepared by the self-assembly of either 3-mercaptopropionic (HSC2COOH) or 8-mercaptooctanoic (HSC7COOH) acids on golds. However, the adsorption was optimized by using the more hydrophobic polyelectrolyte (VC11) and the longer thiol (HSC7COOH). The gradual deprotonation of the HSC7COOH monolayer in the pH range 6-11 enhances the adsorption of the VC11 polyelectrolyte. From these data, an apparent pKa of ∼8 for the monolayer -COOH groups was obtained. The overall degree of packing of the viologen subunits at the monolayer - solution interface was found to be rather poor. The combined monolayer - polyelectrolytes interfacial structures did not block effectively the reduction or dissolved Ru(NH3)63+ ions on the underlying gold electrode.
|Original language||English (US)|
|Number of pages||6|
|State||Published - Oct 16 1996|
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Surfaces and Interfaces