Deconstruction of unsaturated polymers through photo-mediated oxidation under O2

While oxidative cleavage has been a well-known strategy to degrade unsaturated polymers, most processes require harsh conditions and/or expensive oxidizing agents. Using O₂ to degrade polymers is highly desirable, but no reported process is well controlled for the chemical recycling of polymers. Here, we report a photo-mediated oxidative degradation process for unsaturated polymers under O₂ using an earth-abundant Mn catalyst, and the process is demonstrated with polybutadiene, polydicyclopentadiene, and dehydrogenated polyethylene. Nonactivated internal alkenes in these polymers can be effectively cleaved without elevated temperature or pressure. The oxidation process generates acetal as the main functionality, which can be used for further recycling. As a proof of concept, the oligomers with acetal end groups, resulting from the oxidation of polybutadiene, are shown to undergo transacetalization with polyols to form a polymer network. The oxidation process demonstrated here holds promise for the recycling of hydrocarbon polymers under mild conditions in a cost-effective fashion.