Self-assembled monolayers and electrostatically self-assembled multilayers of polyalkylviologens on sulfonate-modified gold and indium-tin-oxide electrodes.

Self-assembly (SA) of polyviologens with linear alkyl spacers PVn (n = 3-10) on sulfonate-primed gold and ITO electrode surfaces has been investigated by CV, QCM, XPS and AFM. The polymers form stable and relatively dense monolayers even from 10-4 M PVn concentration. The viologen surface density is decreased as n is increased but for n = 10 and on alkylsulfonate-primed surfaces a strong adsorption takes place, with decreased redox potential and very narrow cyclic voltammogram of the absorbed layer due to organized structures on the surface. Stable and regular electrostatically self-assembled (ESA) multilayers are built on sulfonate-primed surfaces with PV3 and polysulfonates. From XPS analysis the composition of the PVn/polysulfonate multilayers corresponds to a 1:1 ratio of polyanion and polycation charges, i.e. no extra non polymeric ion is present, independently from the alkane chain length. The rate of electron transfer within the multilayers (diffusion coefficient = ca 10-9 cm2 s-1) is higher than for analogous bulk materials.