Coadsorption of a polyanion and an azobenzene dye in self-assembled and spin-assembled polyelectrolyte multilayers

We describe the integration of a photochromic azobenzene dye into electrostatically bound polyelectrolyte multilayers. Two different deposition techniques are compared: electrostatic self-assembly (ESA) and polyelectrolyte spin-assembly. The polyelectrolytes used were PEI (polyethylenimine) and PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt]). Successful incorporation of the azobenzene dye Direct red 80 (DR80) into ESA and spin-assembled multilayered films (PEI/DR80) is demonstrated. We find that coadsorption of DR80 and PAZO on a PEI surface occur in different proportions and packing densities, depending on the assembly technique selected. We find that using DR80 as a coadsorbing agent can dramatically enhance the rate of PAZO adsorption, and we observe different deposition rates for DR80 and PAZO when the two materials adsorb simultaneously from a common solution.