Bio-based dynamic network engineering of aminated lignin for strong, tough, and self-healing polyurea elastomers

Achieving a favorable balance between mechanical robustness and room-temperature self-healing remains challenging for polyurea elastomers because network reinforcement often restricts the chain mobility required for repair. To improve this balance, this study has established a dual dynamic network in which Mannich-aminated lignin serves as a multifunctional reactive node within a disulfide-containing polyurea matrix. Compared with unmodified lignin, aminated lignin exhibits improved compatibility and participates in network formation, generating rigid reinforcing domains with abundant hydrogen-bonding sites. Meanwhile, dynamic disulfide bonds enable reversible covalent exchange, network rearrangement and additional energy dissipation. The optimized TL-PUA-7.5 composite achieves a tensile strength of 11.16 MPa, a toughness of 85.34 MJ m^-3 and an elongation at break exceeding 1200%, with the strength and toughness reaching 452% and 500% of those of neat polyurea. Structural and morphological analyses indicate uniform lignin dispersion and close interfacial integration. The enhanced mechanical performance arises from lignin reinforcement and efficient stress transfer. Dynamic disulfide exchange and hydrogen bonding enable room-temperature healing, with tensile strength recovery of 98.7% for TL-PUA-5.0 and 93.9% for TL-PUA-7.5 after 24 h. The lignin-containing network further exhibits enhanced UV-aging resistance and UV-associated strengthening, together with improved hydrophobicity and chemical resistance. As a proof of concept, TL-PUA-7.5 was used as an encapsulation matrix for a flexible strain sensor that exhibited stable cyclic responses.