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Covalent adaptable networks (CANs) possess multiple functions including reprocessing (or recyclability), self‐healing, welding, shape shifting, 3D printing, etc., due to the network rearrangement from dynamic bonds, and favorable performance from their cross‐linked feature, and they are supposed to be as sustainable alternatives to thermosets. However, the thermal and mechanical properties, and stability of CANs are often sacrificed for rapid network rearrangement. In this paper, fast‐reprocessing CANs with high performance are facilely constructed by in situ polymerization and dynamic cross‐linking of styrene (St), maleic anhydride (MA), and acetal diol (BHAD). The rigid and hydrophobic polymer backbone endow the materials with high glass transition temperatures, mechanical performance, and water resistance. Besides, carboxylic group‐catalyzed dual dynamic ester and acetal‐based networks exhibit faster stress relaxation and realize extrusion reprocessing. This work provides an ingenious and simple strategy of construction of CANs combining rapid network rearrangement and excellent comprehensive performance, which is beneficial for the application of CANs. [ABSTRACT FROM AUTHOR]

Polyurethane (PU), as a polymer material with versatile product forms and excellent performance, is used in coatings, elastomers, adhesives, and foams widely. However, the raw materials (polyols and isocyanates) of PU are usually made using petroleum‐derived chemicals. With the concern for depletion of petroleum resources and the associated negative impact on the environment, developing technologies that can use renewable raw materials as feedstock has become a research hotspot. Lignin, as an abundant, natural, and renewable organic carbon resource, has been explored as raw material for making polyurethanes because it possesses rich hydroxyl groups on its surface. Meanwhile, compared to vegetable oils, lignin does not compete with food supply and performance of the resulting products is superior. Lignin or modified lignin has been shown to impart the polyurethane material with additional functionalities, such as UV‐blocking ability, hydrophobicity, and flame retardancy. However, the utilization of lignin has encountered some challenges, such as product isolation, heterogeneity, aggregation, steric hindrance, and low activity. This paper summarizes recent research progress on utilizing lignin and modified lignin for bio‐based polyurethane synthesis with a focus on elastomers and foams. Opportunities and challenges for application of the lignin‐based polyurethanes in various fields are also discussed. [ABSTRACT FROM AUTHOR]