Selective, Oxygen‐Tunable, and Metal‐Free Functionalization of Polyethylene Through Dual‐Mode Nitrosation and Carbonylation

Polyethylene (PE), the world's most produced synthetic polymer, is highly durable but resistant to chemical modification due to its inert carboncarbon backbone. This work presents a metal-free, nitrosation process for direct CH functionalization of PE, enabling selective formation of oxime- or carbonyl-functionalized polymers. The method operates under mild visible-light conditions in solution and through thermally driven reactive extrusion, making it suitable for both laboratory and industrial applications. The key reagent, tert-butyl nitrite (t-BuONO), produces an alkoxy radical (t-BuONO•) for CH activation and a persistent nitrosyl radical (NO•) that installs ketoxime functionalities. Mechanistic studies using quantum yield determination and time-resolved transient absorption spectroscopy confirm the energy-transfer activation of t-BuONO and hydrogen atom transfer pathways. Unlike previous strategies, this approach yields pure oxime or keto-functionalized PE's without metals or pre-functionalization. Moreover, oxime groups serve as intermediates convertible into esters, ethers, or urethanes, allowing control over polymer polarity and thermomechanical properties. Together, this strategy transforms a venerable small-molecule transformation into a scalable, selective, and tunable route for the upcycling of PE, and enables a selective and sustainable route to valorize one of the world's most ubiquitous, but most recalcitrant plastics.