Multifunctional Polyurethane Networks Combining Strength, Toughness, and Fast Autonomous Self-Healing via the Synergy of Multiple Dynamic Bonds

Abstract

Polymeric materials exhibiting concomitant toughness, strength, and autonomous self-healing at room temperature are attractive in many applications. However, the mechanical strength often compromises the self-healing capability, making development of such materials challenging. Here, we developed multifunctional supramolecular polyurethane (PU) based elastomers of high toughness and fast autonomous self-healing capacity at ambient conditions via the synergy of quadruple H-bonds and dynamic boronic ester bonds. The design involves the use of reversible quadruple H-bonding ureido-pyrimidinone (UPy) motifs and soft olefin side chains to endow the elastomer with toughness and chain flexibility to support self-healing. Further cross-linking of the photoreactive olefin groups via dynamic boronic ester bonds by thiol-ene chemistry provided strength while maintaining self-healing at ambient conditions. The resulting elastomers (PU-Enex) showed high toughness (42.8 MJ m–3), strength (11.1 MPa), notch insensitivity, and high fracture energy (23.6 kJ cm–2). Notably, PU-Enex demonstrated fast self-healing at room temperature, recovering almost 90% of their original toughness within 6 h postinjury. Finally, they also exhibited remarkable adhesive strength (1.0 MPa), high optical transparency, and strong blue fluorescence upon UV irradiation. The work demonstrates the development of a novel, multifunctional PU with outstanding mechanical properties and enhanced self-healing at ambient conditions, enabling an exciting range of new applications.