A Strategy of Thiolactone Chemistry to Construct Strong and Tough Self-Healing Supramolecular Polyurethane Elastomers via Hierarchical Hydrogen Bonds and Coordination Bonds

Abstract

Self-healing elastomers with extended service life and enhanced reliability have attracted extensive attention in recent years due to their broad application in fields such as protective coatings, wearable electronics, shape memory materials, and health-care monitoring. However, it is challenging to simultaneously optimize the mechanical properties (strength and toughness) and self-healing capacity of the elastomers. Herein, thiolactone chemistry was delicately used as a bridge to address this conundrum by incorporating 2-ureido-4[1H]-pyrimidinone (UPy) motifs and imidazole ligands into the side chains of linear polyurethane. The synergistic cross-linking of UPy H-bonds and Zn2+-imidazole coordination afforded a robust supramolecular network to significantly improve the strength. Meanwhile, these dynamic cross-linking points acted as sacrificial bonds for energy dissipation under external stress, which played a dominant role in toughening. Therefore, the resultant elastomer (PU-Im-UPy-Zn) exhibited a tensile strength of 9.1 MPa, a breaking elongation of 989%, and toughness up to 62.1 MJ m–3. In addition, the reversible exchange of hierarchical hydrogen bonds (single H-bonds between the carbamate groups and quadruple H-bonds of the UPy dimers) and coordination bonds as well as the high mobility of side chains were conducive to repairing under mild conditions. The superficial scratches completely disappeared at 60 °C, and a satisfactory healing efficiency of 78% was observed after 24 h. This work provides some insights into future design of self-healable supramolecular polyurethane elastomers integrated with conspicuous strength and toughness.