Highly elastic and degradable vitrimeric elastomers using polycondensation

Strengthening and Toughening Dynamic Covalent Thermosets via Hydrogen-Bonded Cross-Links

“…Due to the three-dimensionally cross-linked structures, thermosets generally provide high strength and stiffness, structural stability, and resistance to abrasion and solvents, playing irreplaceable roles in many fields such as electronic packaging, coatings, adhesives, additive manufacturing, and composites. Nevertheless, thermosets cannot be recycled after their initial formation owing to the permanent covalent cross-links, leading to increasing plastic wastes and environmental pollution. − An elegant strategy to turn cross-linked polymer networks into recyclable plastics is to replace the covalent cross-links by dynamic covalent bonds, giving rise to the formation of dynamic covalent thermosets. − Dynamic covalent bonds are usually dormant at ambient conditions but capable of dynamically exchanging under stimuli (e.g., heat, light, pH). − Hence, dynamic covalent thermosets behave like traditional thermosets at ambient conditions but display thermoplastic properties under stimuli, endowing the dynamic covalent thermosets with recyclability. − However, similar to the traditional thermosets, dynamic covalent thermosets always suffer from the unfavorable trade-off between their strength/stiffness and ductility/toughness. Those with high tensile strength (e.g., >40 MPa) and Young’s moduli (e.g., >1.0 GPa) are generally fragile because of the very low elongation at break (<10% in most cases), − whereas the highly ductile ones generally exhibit relatively low tensile strength and Young’s moduli. , This is because the mechanical strength/stiffness can be effectively enhanced by increasing the dynamic covalent cross-linking degree, which however naturally suppresses the polymer chain mobility and extensibility, leading to decreased ductility and toughness. , Therefore, there is a significant need to reconcile the trade-off between strength/stiffness and ductility/toughness of dynamic covalent thermosets to expand their practical utility.…”

High-Performance Biobased Elastomers with Both High Strength and High Toughness

“…Elastomers exhibiting high strength and high toughness are essential in both traditional engineering and cutting-edge research fields. − Although the demand for robust and tough elastomers continues to grow, their long-term environmental impact has been recognized as an important issue . Traditional strategies involve the use of covalent chemical cross-linking in the preparation of thermoset elastomers.…”