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Circularity in Mixed Plastics Chemical Recycling Enabled by Variable Rates of Polydiketoenamine Hydrolysis

preprint
submitted on 17.03.2021, 05:26 and posted on 19.03.2021, 07:19 by jeremy demarteau, alexander epstein, Peter Christensen, Mark Abubekerov, hai wang, Simon J Teat, Trevor Seguin, Christopher Chan, Corinne D. Scown, Thomas Russell, Jay Keasling, Kristin Persson, Brett Helms
Footwear, carpet, soft furnishings, automotive interiors, and multi-layer packaging are examples of products manufactured from several types of polymers whose inextricability poses significant challenges for recycling at end-of-life. Here, we show that chemical circularity in mixed-polymer recycling becomes possible by controlling the rates of depolymerization of polydiketoenamines (PDKs) over several orders of magnitude through molecular engineering. Stepwise deconstruction of mixed-PDK composites, laminates, and assemblies is chemospecific, allowing a prescribed subset of monomers, fillers, and additives to be recovered in pristine condition at each stage of the recycling process. We provide a theoretical framework to understand PDK depolymerization via acid-catalyzed hydrolysis and experimentally validate trends predicted for the rate-limiting step. The control achieved by PDKs in managing thermal and materials entropy points to new opportunities for pairing circular design with sustainable manufacturing.

Funding

U.S. Department of Energy Contract No. DE-AC02-05CH11231

U.S. Department of Energy (DOE) Bioenergy Technologies Office award number 1916-1597

Berkeley Research Computing program at the University of California, Berkeley

Grant No. NIH S10OD023532

National Science Foundation Graduate Research Fellowship under Grant No. DGE 1752814

History

Email Address of Submitting Author

bahelms@lbl.gov

Institution

Lawrence Berkeley National Laboratory

Country

USA

ORCID For Submitting Author

0000-0003-3925-4174

Declaration of Conflict of Interest

BAH and PRC are inventors on US provisional patent application 62/587,148 submitted by Lawrence Berkeley National Laboratory that covers polydiketoenamines, as well as aspects of their use and recovery.

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