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

ABSTRACT 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.