Fulvenyl-Functionalized Polyisocyanides: Redox-active (Cross-) Conjugated Polymers as Materials for Organic Polymer Batteries and Electrochromic Diodes

• Applicant: Privatdozent Dr. Frank Pammer
• Subject Area: Polymer Materials ; Synthesis and Properties of Functional Materials ; Preparatory and Physical Chemistry of Polymers
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 282201761

The research project is aimed at combining the properties of fulvenes and polyisocyanides (PICs), in order to access a new type of reversibly redox-active conjugated polymer that may serve as charge storage material in organic polymer batteries, or as redox-active dye in electrochromic diodes. Polyisocyanides are formally conjugated polymers that consist of a backbone of sp2-hybridized carbon atoms. However, the electronic structure of the polymer is such that the carbon atoms within the main-chain are linked by single bonds and are therefore cross-conjugated. As a consequence, electronic effects typically associated with extended conjugation are not observed. However, introduction of redox-active fulvenyl-groups into conjugated side-chains furnishes a polymer in which electrochemical reduction or oxidation may facilitate to a redistribution of the pi-electrons along polymer-backbone, transforming it into a fully conjugated polyacetylene-like pi-system. Ideally, this redox-response will allow to reversibly switch the color of the polymer electro-chemically, e.g. from virtually colorless to black. Furthermore, the introduction of specific redox-active sites allows the polymer to store up to one (1) full charge per repeat unit. For the simplest conceivable systems this corresponds to energy densities of up to 200-300 Ah/kg, which compares favorably e.g. with the classic lead/sulfuric acid battery (177 Ah/kg). Funding will be invested primarily in the preparation of new tria-, penta-, and hepta-fulvenyl functionalized PICs, and their physical, optical, and electrochemical characterization. Preparation of organic electronic devices will be pursued in close collaboration with independently funded cooperation partners.

• DFG Programme: Research Grants