Polyurethane with high mechanical performance and excellent self-healing efficiency enabled by strain-induced crystallization and multiple hydrogen bonds for human motion sensing

Synergistic reinforcement of self-healing elastomers by strain-induced crystallization and multiple hydrogen bonds. • The elastomer achieves a tensile strength of 52.2 MPa, an elongation at break of 1525.1%, and an toughness of 330.05 MJ/m 3 . • After healing at 60 °C for 24 h, the self-healing efficiencies reached 96.6% for stress and 101.7% for strain. • The fracture energy attained 117.65 kJ m −2 . • The flexible composite sensor exhibits strain-sensing, with GF of 1.71 and 1.87 in the 0–100% and 100–300% strain range. The harsh and complex conditions in practical applications have driven a strong demand for polyurethane (PU) elastomers with self-healing functionality. However, achieving both superior mechanical performance and excellent self-healing ability in a single PU elastomer still poses a significant difficulty. In this investigation, a self-healing PU elastomer (PCL-HMPU) with outstanding mechanical performance was developed. The prepared self-healing PU elastomer demonstrated a superior tensile strength of 52.2 MPa, an elongation at break of 1525%, and an outstanding toughness of 330.05 MJ/m 3 . Specifically, the symmetric Methylene-bis(4-cyclohexylisocyanate) (HMDI) and semi-crystallizable poly(caprolactone) diol (PCL) enable strain-induced crystallization (SIC) under large deformation, thereby providing a self-reinforcement effect. The acylsemicarbazide moieties (ASCZ) and disulfide bonds in 3,3′-dithiobis(propionohydrazide) (DPH) impart the self-healing capability, enabling the elastomer to recover 96.6% of its tensile strength and 101.7% of its tensile strain after 24 h at 60 °C. The amorphous structure of PCL-HMPU facilitates self-healing, while the SIC and ASCZ collaboratively enhances its mechanical performance. Moreover, based on the favorable compatibility between PCL and the ionic liquid, a high-performance ionic skin was fabricated, further highlighting the potential of PCL-HMPU for flexible electronics.