Self-Healing and Reprocessable Cross-Linked Polyurethane Urea With High Strength and Modulus via Dynamic Disulfide Bonds

To achieve high strength and modulus of thermosetting polyurethane materials at room temperature, and self-healing and reprocessing at elevated temperatures, this study proposes a dynamic covalent crosslinking strategy where disulfide bonds are predominantly located in the rigid hard segments of crosslinked polyurethane urea (C-PUUSS). The resulting polyurethane urea exhibits outstanding fracture toughness (157.2 MJ·m −3 ), tensile strength (60.9 MPa), elongation at break (479%), and a remarkable Young's modulus (235.4 MPa). Despite its crosslinked structure, C-PUUSS demonstrates good reprocessability and self-healing capability due to disulfide bonds. Compared with the pristine sample, the reprocessed C-PUUSS retains nearly unchanged tensile strength, while its elongation at break and toughness increase, with a slight decrease in Young's modulus. The self-healing efficiencies of tensile strength and elongation at break for C-PUUSS are 61.7% and 61.9%, reflecting the inherent trade-off of thermosetting networks: high crosslink density brings excellent mechanical properties but inevitably restricts chain mobility and slows the exchange of dynamic bonds. Moreover, the reprocessed C-PUUSS maintains favorable self-healing performance. In addition, C-PUUSS exhibits excellent solvent resistance. This study achieves a synergy of high crosslinking density, self-healing, and reprocessability through molecular design, offering a novel approach for the development of sustainable high-performance polyurethane materials.