Electrochemical preparation and properties of composite films with polypyrrole/poly(styrene sulfonate): polyviologen multilayers

Multilayers consisting of polypyrrole/poly(styrene sulfonate) (PP/PSS) and polyviologen (PV) were electrochemically prepared on Au to enhance long-ter m and environmental (e.g., pH) stability of PV modified electrodes. PV cati onic polyelectrolytes were adsorbed on top of electrochemically synthesized PP/PSS via electrostatic interactions with PSS present at the surface of c onducting polymer substrates. By alternating electrochemical synthesis of P P/PSS and PV adsorption in a single medium, multilayers were prepared up to 13 layer-pairs. The electrochemical and electrochromic properties of multi layers produced in this way were quite reproducible, since the film prepara tion does not require medium changes and the layer thicknesses can be finel y controlled using the applied potential and time. Although the redox poten tial of PP/PSS shifted in the positive direction with increase in the numbe r of layer-pairs, cyclic voltammograms of multilayers indicated that total electroactivity of PP/PSS was retained. PV molecules, sandwiched between re duced PP/PSS layers, were also fully electroactive and quite stable during repeated redox switching processes, indicative of enhanced long-term stabil ity. Multilayers also possessed electrochromic properties which were direct ly proportional to the number of PV layers.