The nature of charge transfer in non-conjugated redox active polymers is an area of active interest. Previous work examined the role of pendant spacing along the backbone chain by synthesizing spatially defined polymers with varied spacing between activated ester pendants via acyclic diene metathesis (ADMET). These polymers were then post functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino TEMPO) to afford a series of spatially defined TEMPO containing polymers. This study showed that glass transition temperature (T_g) directly correlated to charge transfer abilities, and further identified the n = 6 backbone as the ideal spacing due to having the lowest T_g and the fastest electron transfer kinetics. Building upon these results, we examine how backbone spacing affects different redox polymers. To that end, we utilized our previously identified n = 6 spacing activated ester polymer as a template for synthesizing multiple redox active polymers, each with a different redox pendant. The newly prepared polymers exhibited large variations in their physical properties (e.g., T_g and solubility), highlighting how pendant choice greatly influences properties despite having the same backbone. Electrochemical properties of the polymers were probed in the solution state using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Polymer diffusion was measured using diffusion ordered spectroscopy NMR. While no correlation was found between diffusion and electrochemical performance, this work showcased the usefulness and versatility of the activated ester polymer template for creating spatially defined functional polymers.

Cartoon showing electron hopping between redox units on the polymer backbone.

Chen Wang

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