A Modular Post-Polymerization Modification Route to Aminated Polybutadienes for Electrochemical CO₂ Valorization

Post-polymerization modification can provide access to functional polymers that are difficult to obtain through bottom-up synthesis, allowing systematic tuning of the material properties. Such functional polymers, in turn, offer a powerful platform for tailoring catalytic microenvironments, particularly in the electrochemical CO₂ reduction reaction (CO₂RR), where tunable CO₂ adsorption and mass transport are critical for selectivity and efficiency. However, achieving precise control over these properties requires accurate inclusion of functional groups on the polymer backbone, which remains a significant challenge. Here, we report a modular post-polymerization approach to functionalize polybutadiene, leveraging the reactivity of the unsaturated bonds, through nitration and subsequent reduction to primary amines. Using tert-butyl nitrite as a simple and inexpensive NO₂ radical source, we achieve tunable and regio- and stereoselective nitro incorporation onto the polymer backbone ranging from 0.8 to 18.6% (nitro per 100 carbon atoms), which could be readily reduced to the primary amine without compromising the polymer backbone integrity. Detailed polymer analysis after ¹⁵N-labeling revealed a high regioselectivity for the functionalization of the internal over terminal unsaturated bonds. When applied as an amine-functionalized layer on a Cu electrode for CO₂ electroreduction, we observed a scaling relationship between the amine functionalization degree and the partial current for C₂ products (ethylene and ethanol). Overall, this work highlights a robust and versatile post-polymerization strategy that advances precision control in polymer functionalization essential for engineering applications, particularly in energy materials.