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.