A “Polymer to Polymer” Chemical Recycling of PLA Plastics by the “DE–RE Polymerization” Strategy

Yang, Rong; Xu, Guiying; Dong, Bingzhe; Hou, Hongbin; Wang, Qinggang

doi:10.1021/acs.macromol.1c02085

Cited by 63 publications

(38 citation statements)

References 61 publications

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“…Our research group is committed to finding out versatile depolymerization catalysts to achieve the degradation of various polymer materials. In our previous studies, we found that zinc bis[bis(trimethylsilyl)amide] [Zn(HMDS) 2 ], as a multifunctional transesterification catalyst, can promote the chemical recycling of PLA and PCL to value-added chemicals. − Based on that, in this work we further broaden the application fields for the selective catalysis depolymerization of plastic materials, including PLA, BPA-PC, PBS, PBAT, PCL, and PET. The degradation processes and influencing factors of a single polyester and polycarbonate plastics were explored first.…”

Section: Introductionmentioning

confidence: 93%

Selective, Sequential, and “One-Pot” Depolymerization Strategies for Chemical Recycling of Commercial Plastics and Mixed Plastics

Yang

Dong

et al. 2022

ACS Sustainable Chem. Eng.

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The commercial plastics that are currently used in large-scale are primarily concerned with performance and durability, rather than degradability and recyclability. As a result, the chemical recycling of plastics becomes a significant challenge. Selective depolymerization of the mixed plastic waste is a promising solution to the challenges caused by plastic accumulation. Here we present sequential and "one-pot" depolymerization strategies for chemical recycling of commercial plastics (PLA, BPA-PC, PBS, PBAT, PCL, and PET) and mixed plastics (BPA-PC/ PET, PLA/PBS, and PLA/PBAT) to their initial monomers or value-added chemicals. Taking advantage of the differences in depolymerization reactivity of commercial plastics and versatile catalytic degradation ability of zinc bis[bis(trimethylsilyl)amide] [Zn(HMDS) 2 ], the selective depolymerization process was smoothly achieved under mild conditions. These strategies provide ideas for promoting the sustainable development of plastics that are currently being used in large-scale.

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Section: Introductionmentioning

confidence: 93%

Selective, Sequential, and “One-Pot” Depolymerization Strategies for Chemical Recycling of Commercial Plastics and Mixed Plastics

Yang

Dong

et al. 2022

ACS Sustainable Chem. Eng.

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“…The chemical recycling of polymers has been extensively explored, but most examples involved downcycling to produce low-molecular-weight chemicals without value-added applications. − The widely explored examples included poly(ethylene terephthalate) (PET) (into versatile chemicals), − polylactic acid (PLA) (into lactic acid and its derivatives), , and even polyethylene (into useful liquid fuels and waxes). − In addition to the one-way chemical recycling of commodity polymers, there are numerous studies on the so-called chemically recyclable polymers with closed-loop life cycles, which can undergo a reversible polymerization/depolymerization process to realize full polymer recycling under mild conditions. − Many well-known examples of such closed-loop recycling polymers were associated with five-membered ring monomers, such as γ-butyrolactone (γBL). ,− However, the ring-opening polymerization (ROP) of five-membered ring monomers was challenging and difficult to control due to the thermodynamically stable monomer structure. Therefore, monomers with fused-ring structures were designed to modulate the ring strain energy and facilitate the reversible polymerization/depolymerization processes. ,, Moreover, the introduction of the fused ring can improve the thermal and mechanical properties of the obtained polymers for practical applications.…”

Section: Introductionmentioning

confidence: 99%

Chemical Upcycling of Poly(3-hydroxybutyrate) into Bicyclic Ether–Ester Monomers toward Value-Added, Degradable, and Recyclable Poly(ether ester)

Shen

2022

ACS Sustainable Chem. Eng.

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The chemical recycling of plastic wastes into value-added products is an attractive strategy to reduce the consumption of fossil fuels and reduce the plastic pollution. We report here the facile upcycling of poly(3-hydroxybutyrate) (P3HB) into value-added polymerizable monomers and subsequent polymerization toward degradable and recyclable polymers. The bicyclic monomer 4-methyloctahydro-2H-benzo[b][1,4]dioxepin-2-one (4-MOHB) was first synthesized from P3HB through efficient steps. The obtained monomers underwent bulk ring-opening polymerization (ROP) catalyzed by stannous octoate (Sn(Oct)2) to give the amorphous materials. With benzyl alcohol (BnOH) as an initiator, Sn(Oct)2 can effectively catalyze the ROP of bicyclic ether–ester monomers in a controllable fashion. Moreover, poly(4-methyloctahydro-2H-benzo[b][1,4]dioxepin-2-one) (P(4-MOHB)) showed a closed-loop recovery property due to the fused bicyclic monomer structure. The selective depolymerization of the P(4-MOHB) homopolymer back to 4-MOHB monomer can be easily realized using p-toluenesulfonic acid (TsOH) or Sn(Oct)2 as a catalyst in solution or in bulk. This strategy to recycle bioplastics into value-added materials has a promising application prospect and is beneficial to extend the life cycle of environment-friendly materials.

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“…However, even at these decreased temperatures, epimerization reactions occur to a significant degree, resulting in crude LLA with a meso ‐LA content of 4–11 % at only 73 % conversion of the prepolymer [12] . Together with elimination reactions generating acrylic acid, these side reactions affect the purity of the crude LA formed and subsequently the final yield [26a, 27] . As stated, the high recycling temperature for PLA is inherent to the high T c of LA.…”

Section: Introductionmentioning

confidence: 99%

“Like Recycles Like”: Selective Ring‐Closing Depolymerization of Poly(L‐Lactic Acid) to L‐Lactide

et al. 2022

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Chemical recycling of poly(L‐lactic acid) to the cyclic monomer L‐lactide is hampered by low selectivity and by epimerization and elimination reactions, impeding its use on a large scale. The high number of side reactions originates from the high ceiling temperature (Tc) of L‐lactide, which necessitates high temperatures or multistep reactions to achieve recycling to L‐lactide. To circumvent this issue, we utilized the impact of solvent interactions on the monomer–polymer equilibrium to decrease the Tc of L‐lactide. Analyzing the observed Tc in different solvents in relation to their Hildebrand solubility parameter revealed a “like recycles like” relationship. The decreased Tc, obtained by selecting solvents that interact strongly with the monomer (dimethyl formamide or the green solvent γ‐valerolactone), allowed chemical recycling of high‐molecular‐weight poly(L‐lactic acid) directly to L‐lactide, within 1–4 h at 140 °C, with >95 % conversion and 98–99 % selectivity. Recycled L‐lactide was isolated and repolymerized with high control over molecular weight and dispersity, closing the polymer loop.

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A “Polymer to Polymer” Chemical Recycling of PLA Plastics by the “DE–RE Polymerization” Strategy

Cited by 63 publications

References 61 publications

Selective, Sequential, and “One-Pot” Depolymerization Strategies for Chemical Recycling of Commercial Plastics and Mixed Plastics

Selective, Sequential, and “One-Pot” Depolymerization Strategies for Chemical Recycling of Commercial Plastics and Mixed Plastics

Chemical Upcycling of Poly(3-hydroxybutyrate) into Bicyclic Ether–Ester Monomers toward Value-Added, Degradable, and Recyclable Poly(ether ester)

“Like Recycles Like”: Selective Ring‐Closing Depolymerization of Poly(L‐Lactic Acid) to L‐Lactide

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