Manufacturing of ultra-thin redox-active polymer films using the layer-by-layer method and co-polymerization of vinyl viologen units

The current study presents the principle of a new approach to fabricating redox-active polymers film on mesoporous TiO$_{2}$ electrodes. This new strategy involves the top-down approach (adsorption) combined with bottom-up layer-by-layer (LbL) crosslinking and “in situ” co-polymerization reactions. This approach uses 4,4$^{\prime }$-bipyridinium units, so-called viologen with an anchoring phosphono ethyl acid and the vinyl group as building blocks molecules, and 1,3,5-tris-(bromomethyl) benzene as crosslinker. Crosslinking and co-polymerization reactions lead to the growth of the concentration of redox species on the surface and increased stability of the colored areas towards forced desorption in water. The method offers a simple, versatile way to manufacture nanostructured functional materials.