Sustainable developments in polyolefin chemistry: Progress, challenges, and outlook

Polyolefins are the largest-scale synthetic plastics and play a key role in modern society. Their production consumes huge amounts of fossil-derived monomer feedstocks, which unfortunately became discarded wastes after use with a very low recycling ratio, causing severe environmental pollution and huge consumption of non-renewable resources. This lack of sustainability could in principle be solved by reusing the waste polyolefins repeatedly as virgin materials or recovering olefin monomers for re-entering the polyolefin cycle. However, it is challenging due to their chemical inertness (C-H and C-C bonds) and lack of degradation sites along the polyolefin chains. Therefore, to make polyolefins more sustainable, degrading or modifying the waste polyolefins on large scales could facilitate their reuse as virgin polyolefins or recovery to polymerizable feedstocks, rethinking the design and synthesis from monomer feedstocks could afford inherently recyclable and thus more sustainable polyolefin or polyolefin-like materials. Given the above, this review will introduce recent progress in the rapidly advancing field: 1) Recycling and upcycling to fuels and other small molecule products, olefin monomer, telechelic products, reprocessable and functional polyolefin materials; 2) Increasing sustainability by the de novo design and synthesis of new degradable and reprocessable polyolefin and polyolefin-like polymers.