Electrochemical Versatility of Soluble Redox Active Polymers

Organic redox-active materials offer advantages of material tunability while maintaining high performance for next-generation energy storage and conversion solutions. Macromolecular architectures such as polymers, colloids, and oligomers have recently gained interest for their size-exclusion capabilities. Redox Active Polymers (RAPs) have traditionally been electrochemically studied as films or composites [1], with few examples of solution-phase studies until recent years [2]. Soluble RAPs have begun emerging as viable active materials for energy storage solutions such as size-exclusion flow batteries [3-4]. Our laboratories have introduced several redox active motifs used as pendants on these soluble RAPs in recent years [3]. Their introduction into the field of energy storage as fluid energy carriers has elucidated some of their reactivity and applicability, yet detailed characterization of their complex charge transfer mechanisms and their interactions in solution and with catalytic and photocatalytic interfaces has not been fully addressed. In this talk, I will highlight advances in characterizing the redox activity of these polymers and their behavior at electrode interfaces with the aim of using them as versatile redox fluids. I will also describe how their charge transfer mechanisms make them ideal for varied energy storage applications beyond size-exclusion redox flow batteries. The RAPs are evaluated using analytical techniques such as potential-controlled electrolysis, spectro-electrochemistry, and voltammetric methods including transient and steady-state methods. Additionally, comparisons to the small molecule counterparts of the RAP active units aid to understand the differences observed when redox active centers are tethered to a chain containing hundreds of pendants. I will discuss how this new type of soluble RAPs interact with energy conversion electrodes and how charge transfer and transport within RAP particles facilitates catalytic processes associated with energy storage. [1] J. Am. Chem. Soc. 1978, 100, 4248. [2] J. Am. Chem. Soc. 2018, 140, 2093. [3] Acc. Chem. Res. 2016, 49, 2649. [4] J. Am. Chem. Soc. 2014, 136, 16309.