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Abstract Synthetic plastics sourced from petroleum have gained widespread use since the 1950s. Polystyrene (PS) is one of the most extensively used plastics, as it is colorless, has high mechanical strength, and exhibits excellent chemical and thermal stability; however, it is also one of the least recycled plastics because of the high cost and low profit in recycling. Herein, we demonstrate a mechanochemical recycling approach that allows PS to be efficiently degraded into benzene when it is ground in a ball mill with AlCl3. For example, when 165 kDa PS pellets are milled with AlCl3, the extent of degradation reaches 90% at 15 min. Isotope labeling experiments indicate that both ambient water and the polymer backbone can be proton sources for the formation of benzene. The benzene generated in the mechanochemical degradation can be used to synthesize styrene, which can be repolymerized to produce polystyrene, allowing for the closed‐loop recycling of PS. In addition, a mechanochemical Friedel–Crafts acylation between the generated benzene and the subsequently added benzoic anhydride produces benzophenone in 40%–50% yield. The mechanochemical degradation process demonstrated here is solvent‐free, cost‐effective, and energy‐efficient, providing a promising route for the chemical recycling and upcycling of PS.
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Mechanochemical Degradation and Recycling of Synthetic Polymers
Abstract The accumulation of plastic waste, due to lack of recycling, has led to serious environmental pollution. Although mechanical recycling can alleviate this issue, it inevitably reduces the molecular weight and weakens the mechanical properties of materials and is not suitable for mixed materials. Chemical recycling, on the other hand, breaks the polymer into monomers or small‐molecule constituents, allowing for the preparation of materials of quality comparable to that of the virgin polymers and can be applied to mixed materials. Mechanochemical degradation and recycling leverages the advantages of mechanical techniques, such as scalability and efficient energy use, to achieve chemical recycling. We summarize recent progress in mechanochemical degradation and recycling of synthetic polymers, including both commercial polymers and those designed for more efficient mechanochemical degradation. We also point out the limitations of mechanochemical degradation and present our perspectives on how the challenges can be mitigated for a circular polymer economy.
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- Award ID(s):
- 2204079
- PAR ID:
- 10450525
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 62
- Issue:
- 27
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/anie.202300768
