Plastics are essential to modern life, yet their chemical stability has led to persistent

challenges in waste management and environmental accumulation. Chemical recycling offers

a promising route to regenerate virgin-grade materials, while upcycling provides

opportunities to transform waste into products with enhanced performance. Hydrogen atom

transfer (HAT) provides a versatile platform that can drive depolymerization or upcycling

depending on conditions, without requiring preinstalled chain ends that limit scalability and

sustainability.

Here, we present a HAT-driven approach to achieve thermally triggered depolymerization

under conditions that avoid photochemical activation and chlorinated solvents. This method

not only eliminates the need for light sources but also demonstrates high efficiency at

elevated polymer concentrations, moving closer to industrially relevant scenarios. Beyond

recycling, the inherent flexibility of HAT chemistry opens opportunities to tailor monomer

recovery and enable selective bond transformations that support future upcycling strategies.

Overall, hydrogen atom transfer emerges as a broadly applicable tool to expand the chemical

space of circular polymer technologies.

Possible routes of recycling through hydrogen atom transfer (HAT) chemistry.

Krzysztof Matyjaszewski

Carnegie Mellon University