Functional Polymers and Nanoparticles for Sustainable Reaction Control in Electrosynthesis

• Applicant: Professor Dr. Robert Francke
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Organic Molecular Chemistry - Synthesis and Characterisation ; Preparatory and Physical Chemistry of Polymers
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405986400

Organic electrosynthesis is often described as “green” or “intrinsically sustainable”. However, this assessment cannot be readily generalized, since large amounts of (often hydrophobic) supporting electrolytes must be used, which are difficult to remove after electrolysis. The same applies to high mediator loadings, which are often needed to control selectivity. The present renewal proposal addresses these challenges and aims to advance a strategy for sustainable reaction control that was elaborated in the first project stage. The approach involves the use of so-called polymediators and polyelectrolytes. Their difference in size relative to typical product molecules enables recovery by dialysis or membrane filtration. The concept was successfully established by us using TEMPO-mediated anodic oxidation of alcohols as a test case. Our studies also provided insights into the mechanisms of the processes involved and the influence of the molecular weight of the polymers. The second stage of the project is intended to further advance the developed approach. Both a deeper mechanistic understanding as well as extension and optimization of the concept will be targeted. First, the strategy will be extended by including electrochemically stable polymer-supported bases. Such polybases may become useful as proton scavengers in TEMPO-mediated alcohol oxidation and in a variety of other anodic syntheses. In the next step, the scope will be broadened by developing new synthetic applications. For this purpose, polymethacrylate active esters will serve as a flexible platform for the preparation of new polymediators via post-polymerization functionalization. Another key question is how the spatial arrangement of the mediator units affects charge transport and catalytic activity. Our previous work has been based on polymer chains, which tend to have a randomly coiled conformation in solution. In this regard, it will be interesting to examine whether conformational changes can affect the catalytic activity of a polymediator. For this purpose, dendrimer structures exhibiting a rigid spherical conformation in which all mediator units are exposed to the solution will be investigated. Finally, an adjacent topic will be explored to provide new impetus for future research. In this context, the use of dispersed nanoparticles loaded with mediators and supporting electrolyte units is planned. To ensure good electron transfer kinetics between mediator and electrode, the use of electrically conductive carbon nanotubes is proposed. The approach should enable the use of simple mechanical separation processes (centrifugation, filtration) without the necessity for using co-mediators.

• DFG Programme: Research Grants