used in traditional applications such as tires, seals, and adhesives, as well as in emerging fields such as shape memory, flexible electronics, robotics and artificial intelligence. [2,3] Despite the crucial role of elastomers, their huge demand raises an important question of how to dispose of the out-of-service elastomers. For example, worldwide production of natural rubber reached almost 13 million metric tons in 2020, [4] and approximately three billion natural rubber-based tires were manufactured and purchased. [5] Most of them, however, will end up in incineration, massive landfills or storage facilities, which may ultimately leach pollutants into the ecosystem, posting a significant threat to environment and economy. [5,6] To achieve sustainable development, desirable elastomers should first have long service life, which requires materials with high toughness to resist fracture and high fracture energy to resist crack propagation once fractured. Besides, elastomers should be recyclable, that is they are not permanently crosslinked and can be reprocessed without losing their original properties. [3,7] And finally, elastomers should be degradable, demanding them to be degraded by the enzymatic action of microorganisms and/or destroyed by non-enzymatic processes (e.g., chemical hydrolysis) when needed. It is always easy to achieve one or two of these requirements, but it is challenging to meet all of them. [3,8,9,10] For instance, a biodegradable polyester elastomer was developed from lactones, while the toughness was not high and the covalent crosslinking limited its recyclability. [9] A tough elastomer was designed using mussel-inspired coordination bonds, while it was neither recyclable nor degradable. [10] A recyclable polyurethane elastomer with high toughness and fracture energy was developed by introducing dynamic hierarchical domains into the polymer matrix, while the use of poly(dimethylsiloxane) chain made it non-degradable. [3] Thus, the preparation of novel elastomers that are concurrently tough, recyclable, and degradable remains a rigorous challenge but is highly desirable.In this study, two main factors are considered in order to design elastomers with such properties. First, the polymer backbone: considering the requirements of degradation and toughness, we choose polycaprolactone (PCL). Currently, the preparation of sustainable elastomers mainly focuses on the Elastomers have many industrial, medical and commercial applications, however, their huge demand raises an important question of how to dispose of the out-of-service elastomers. Ideal elastomers that are concurrently tough, recyclable, and degradable are in urgent need, but their preparation remains a rigorous challenge. Herein, a polycaprolactone (PCL) based polyurethane elastomer is designed and prepared to meet this demand. Owing to the presence of dynamic coordination bond and the occurrence of strain-induced crystallization, the obtained elastomer exhibits a high toughness of ≈372 MJ m −3 and an unprecedented fracture energy of ...
