Post-Polymerization Modification of Polyethylene through Photochemical Oximation and Consecutive Ketonization

Abstract

Post-polymerization modification of polyolefins provides access to functional polymers not readily available through bottom-up synthesis, thereby expanding the range of material properties available. Here, we demonstrate the clean and efficient functionalization of polyethylene through the solvent- and catalyst-free photochemical oximation, using t-butyl nitrite as an inexpensive and easy to handle NO radical source. Using various grades of polyethylene, we successfully incorporated oxime, ketone, and nitro groups on the polymer backbone, without radical cleavage or crosslinking. The functionalization degree of the three different functional groups is tuneable depending on the reaction atmosphere and system pressure, and the total functionalization degree can reach up to 2.9%. Detailed analysis of the post-modified polyethylene using 15N labeling revealed that the photochemical oximation preferentially functionalizes the pre-terminal carbon and that the functional groups are randomly spaced along the polymer backbone rather than adjacent. These results underscore the novelty and robustness of this methodology, enabling tailored polyolefins with properties that may expand their applications and potentially improve their recyclability.