Biodegradable Thermoplastic Elastomers Achieved by Unchaining Intrinsic Entropic Elasticity

Abstract Elastomers are key components of structural and functional materials used in daily life and in the industry because of their resilience under large strains. However, resolving the biodegradability‐reprocessability‐elasticity trilemma remains a major challenge, highlighting the urgent need for effective design strategies in the synthesis of biodegradable thermoplastic elastomers. In this study, an “unchaining intrinsic entropic elasticity” strategy is proposed in the design and synthesis of poly(ethylene‐cyclohexanedimethylene succinate) (PECS) of variable repeat unit compositions. This copolyester has a single chain acting simultaneously as a reversible network and physical cross‐linking point, and can be readily synthesized via a simple one‐pot melt polycondensation using 1,4‐cyclohexanedimethanol, ethylene glycol, and succinic acid, which is applicable to both gram and kg scales. The mechanical properties of PECS copolyesters change from plastic to elastic deformation as the ethylene glycol content increases, along with a gradual disappearance of the yielding phenomenon, thus unchaining its intrinsic entropic elasticity. The elastic recovery of the copolyesters reaches up to ≈90% under a strain of 200%, which indicates outstanding fatigue performance. PECS copolyesters can be multiple melt‐reprocessable, and have excellent blood compatibility based on a hemolysis assay, along with outstanding biodegradability. This work has the potential to reduce nonbiodegradable elastomers that lead to plastic pollution.