Hierarchical design strategy for constructing dynamic supramolecular self-healing water-absorbing expansion elastomers

Water-absorbing expansion elastomers have dual waterproof properties of expanding sealing and significant application value in environmental engineering and biomedical fields. However, it has defects such as low mechanical properties, difficulty in self-healing when damaged, and difficulty in recycling and reusing, which seriously limit the reliability and sustainability of material applications. To address this issue, we have developed a dynamically adjustable self-healing polyurethane elastomer through a multi-layered design strategy, which exhibited excellent mechanical properties (17. 89 MPa, 1804 %, 104MJ/m³) and self-healing efficiency (95 %, 60℃/48 h). It was synthesized by two-step method using isophorone diisocyanate (IPDI) and polytetramethylene glycol (PTMEG), introducing chain extenders such as hexanedioic acid, aliphatic disulfide, and 4-hydroxyphenylboronic acid. By combining multiple hydrogen bonds and dynamic covalent networks, the toughness, stress recovery, and energy density of the material were significantly improved. Based on this, the water-absorbing expansion elastomers prepared from the multi-layered self-healing polyurethane elastomer owned recyclability and sustainability. Specifically, the PU4@TPU2–5 % sample exhibited a water absorption swelling rate of 318 % (25 °C/72 h). The new material provides a new perspective for improving the performances on traditional water-absorbing elastomers, polyurethane materials, as well as self-healing functional materials.