Mechanically robust waterborne polyurethane with excellent room temperature self-healing and shape memory performance

Achieving severe damage restoration and the ideal combination of good mechanical properties and healing efficiency are two significant challenges for self-healing materials. In this study, a series of shape-memory, self-healing aqueous polyurethane (SMPU) were synthesized based on the molecular self-assembly design of 5-(2-hydroxyethyl)-6-methyl-2-aminuracil (HMA), 4-aminopyridine (4-APD) and polycaprolactone diol (PCL) moieties. The effects of HMA and 4-APD on mechanical properties, self-healing properties, and shape memory properties of SMPU were investigated. The dynamic crosslinking network generated by quadruple hydrogen bonds and multiple coordination bonds not only consumed strain energy but also promoted rapid re-formation after fracture, resulting in superior self-healing ability (healing efficiency 96.3%), excellent mechanical properties (tensile strength 39.1 MPa and elongation at break 908%) and recyclable capabilities of SMPU. Meanwhile, the SMPU showed a noteworthy shape memory effect; its shape fixation rate and recovery rate could reach 99% and 98%, respectively. The temperature and time dependence of the self-healing process were studied by molecular dynamics (MD), and the self-healing mechanism was clarified further. When SMPU was used for leather finishing, the finished and self-healing samples exhibited excellent wear resistance (wear rating: 4 ∼ 5). These advantageous properties endow SMPU with great potential applied value in leather and other regions.