Redox-controlled release of molecular payloads from multilayered organometallic polyelectrolyte films

Organometallic poly(ferrocenylsilane)s (PFSs) featuring redox responsive ferrocene units in their main chain are prepared and characterized for redox triggered film disassembly and release of molecular payloads. Positively or negatively charged side groups render PFS water soluble and these polyelectrolytes also allow the use of an electrostatic self-assembly process for the fabrication of novel functional supermolecular nanostructures. The layer-by-layer (LbL) electrostatic fabrication approach is utilized to obtain films with different bilayer numbers. The electrochemical behaviour of the multilayers with different thicknesses is recorded by capturing cyclic voltammograms (CVs). Film disassembly (multilayer re-dispersed in water) is performed by exposing the multilayers to the different values of holding potentials, corresponding to partial or full oxidation of PFS. Disassembly kinetics is quantitatively monitored by determining the amount of polymer released from CV experiments, as well as from UV-VIS spectroscopy. The proposed PFS multilayer disassembly mechanism is presented. The morphology of the multilayer films as a function of holding times is monitored by AFM. The release of guest molecules such as fluorescent Alexa dyes incorporated at different depths in the multilayer films is studied by fluorescence spectroscopy.