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- Title
"Like Recycles Like": Selective Ring‐Closing Depolymerization of Poly(L‐Lactic Acid) to L‐Lactide.
- Authors
Cederholm, Linnea; Wohlert, Jakob; Olsén, Peter; Hakkarainen, Minna; Odelius, Karin
- Abstract
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.
- Subjects
CHEMICAL recycling; LACTIC acid; DEPOLYMERIZATION; ELIMINATION reactions; DIMETHYLFORMAMIDE; MOLECULAR weights
- Publication
Angewandte Chemie, 2022, Vol 134, Issue 33, p1
- ISSN
0044-8249
- Publication type
Article
- DOI
10.1002/ange.202204531