One-pot solvent-free recycling of mixed biodegradable plastics to useable polymers with trade-off mechanical properties

Biodegradable polyesters derived from cyclic monomers offer sustainable alternatives with closed-loop recyclability, yet practical implementation of conventional systems like polylactide (PLA) and poly( ε -caprolactone) (PCL) remains hindered by some challenges during depolymerization-repolymerization cycles. Herein, we present a solvent-free recycling strategy for mixed recyclable polyester plastics via catalytic alcoholysis and chain extension, yielding useable copolymer polyurethane (PLA/PCL-PU) with trade-off mechanical properties. Under a high-activity transesterification catalyst (i.e. tetrabutyl titanate), short-chain diol precursors (PLA/PCL-diol) were obtained from PLA and PCL mixtures and subsequently chain-extended with 1,6-diisocyanatehexane. The PLA/PCL-PU with a block copolymeric architecture characterized by diffusion-ordered spectroscopy and 13 C nuclear magnetic resonance exhibits enhanced thermal stability and crystallinity of the PLA segments due to the incorporation of PCL segments. Significantly, the resultant PLA/PCL-PU copolymers deliver good comprehensive mechanical properties with a tensile strength of up to 51.0 ± 0.8 MPa and an elongation at break of maximum 379.4 ± 29.1 %. The recycled materials demonstrate packaging preservation ability and 3D printability, with an outstanding biocompatibility. PLA/PCL-PUs can be depolymerized into the corresponding re-polymerizable monomers, showing chemical recyclability. This one-pot solvent-free recycling approach circumvents traditional depolymerization bottlenecks, offering an eco-friendly and simplified route to convert mixed plastics into high-value materials.