Organocatalyzed chemo-selective one-pot upcycling of polyester-block-polycarbonate

Among various recycling technologies developed, upcycling by catalytic depolymerization to monomers and small molecules is an attractive form of chemical recycling assuring an incentivize large-scale valorization of plastic wastes. A model polyester/polycarbonate block copolymer, cis-(exo,exo)-poly(cyclohexene carbonate/norbornene anhydride)-b-poly(cyclohexene carbonate) (poly(CHO/NA)-b-PCHC), undergoes preferable depolymerization under 4-dimethylaminopyridine (DMAP)/CHO organocatalytic system in light of the diverse degradablity of PCHC and poly(CHO/NA) block accompanying configuration transformation. The degradation is proceeded in three distinct steps: i.e. the PCHC block depolymerizes first, subsequently the PCHC moieties associated with poly(CHO/NA) block degrades, and then poly(CHO/NA) block decomposes. A stereochemical transformation of poly(CHO/NA) block from cis to trans is occurred during the whole degradation stage. The degradation of PCHC block and the configurational transformation of poly(CHO/NA) can be switched on/off by simply altering the depolymerization atmosphere from argon to CO2. The systematic degradation data collected here can be used for the upcycling of polyester-block-polycarbonate.

Automated summary

Upcycling through catalytic depolymerization is an attractive form of chemical recycling that allows for large-scale valorization of plastic wastes. In this study, a model polyester/polycarbonate block copolymer was successfully depolymerized using an organocatalytic system, resulting in both degradation and configurational transformation. The degradation process occurred in three distinct steps and the stereochemical transformation of the polymer block was observed throughout the degradation stage. The findings suggest that the depolymerization and configurational transformation can be controlled by adjusting the depolymerization atmosphere.