A catalytic process for selective depolymerization of hydroxylated polymers into monomers and chemical feedstocks

Background

The field of polymer recycling and upcycling has become increasingly important due to the environmental impact of persistent plastic waste. Conventional plastics, such as polyolefins and phenoxy resins, are widely used in packaging, construction, and consumer goods, but their chemical stability and resistance to degradation have led to massive accumulation in landfills and natural ecosystems. As global plastic production continues to rise, there is a critical need for technologies that can efficiently break down these robust materials into useful chemical feedstocks or monomers, enabling a circular economy where plastics are not just disposed of, but continually reused in new forms.

Current approaches to chemical recycling of plastics face significant limitations. Most established methods, such as pyrolysis, require high temperatures and result in complex mixtures of low-value products, making separation and reuse challenging. Hydrolysis and other depolymerization techniques are generally restricted to specific condensation polymers like PET, leaving the majority of commodity plastics unaddressed. Furthermore, these processes often lack selectivity, operate under harsh conditions, and are incompatible with high molecular weight or insoluble polymers. As a result, existing recycling technologies are unable to efficiently convert most plastic waste into well-defined, high-value chemical building blocks, hindering the development of scalable and sustainable plastic recycling solutions.

Technology

This technology is a visible light-driven catalytic process designed for the selective depolymerization of hydroxylated polymers, such as phenoxy resins and functionalized polyethylene derivatives. Utilizing a system composed of an iridium-based photocatalyst, a Brønsted base, and a hydrogen atom donor, the process activates O–H bonds along the polymer backbone via proton-coupled electron transfer (PCET). This activation generates alkoxy radicals that undergo β-scission, cleaving robust aliphatic C–C bonds and fragmenting the polymer into well-defined alkyl radicals. These radicals are subsequently reduced or functionalized to yield isolable α,ω-difunctionalized products, including aldehydes, diols, and diacids. The process operates efficiently at near-ambient temperatures (35–40°C) under blue LED irradiation and is compatible with a range of high molecular weight polymers, enabling their conversion into valuable chemical feedstocks or monomers for closed-loop recycling.

What differentiates this solution is its unprecedented ability to selectively cleave strong C–C bonds in synthetic polymers under mild, environmentally benign conditions, a feat not achievable with traditional recycling methods that rely on harsh pyrolysis or are limited to specific condensation polymers. The method’s modular catalytic system allows for precise control over product distribution and is effective even at low concentrations of functional groups, making it suitable for a wide substrate scope, including commercial resins and custom-designed copolymers. Furthermore, the process enables the downstream conversion of depolymerization fragments into high-value monomers for new polymer synthesis, supporting a circular materials economy. Its tunability allows for the design of recyclable-by-design materials with tailored thermomechanical properties, and ongoing development of electrochemical variants promises enhanced scalability and sustainability, positioning this technology as a transformative advance in polymer upcycling and waste reduction.

Benefits

• Selective cleavage of strong aliphatic C–C bonds in hydroxylated polymers under mild, visible light-driven conditions
• Efficient depolymerization of high molecular weight polymers into well-defined, isolable monomers and chemical feedstocks
• Operates at near-ambient temperatures (35–40°C), reducing energy consumption compared to traditional recycling methods
• Enables closed-loop recycling by converting polymer fragments into α,ω-difunctionalized monomers suitable for new polymer synthesis
• Tunable polymer properties through controlled incorporation of hydroxylated monomers, allowing design of recyclable-by-design materials
• Compatible with a broad substrate scope including commercial phenoxy resins and functionalized polyethylene derivatives
• Produces predictable, high-value products rather than complex mixtures typical of pyrolysis
• Potential for scalability and sustainability improvements via electrochemical process variants

Applications

• Chemical recycling of plastic waste
• Production of monomers for new polymers
• Closed-loop recycling of phenoxy resins
• Upcycling of hydroxylated polyethylene

Additional info

This catalytic process utilizes visible light-driven proton-coupled electron transfer (PCET) to selectively cleave aliphatic C–C bonds in hydroxylated polymers. Using an iridium photocatalyst, Brønsted base, and thiol-based hydrogen atom donor, it activates O–H bonds to generate alkoxy radicals. These radicals undergo $\beta$-scission, fragmenting polymer backbones into well-defined $\alpha,\omega$-difunctionalized chemical feedstocks. Operating at near-ambient temperatures, this method enables closed-loop recycling of resins and polyolefin derivatives into high-value monomers.