Multifunctional Polyurethane Networks Combining Strength, Toughness, and Fast Autonomous Self-Healing Via the Synergy...

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 multi-functional 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 crosslinking 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-Ene_x) showed high toughness (42.8 MJ m^-3), strength (11.1 MPa), notch-insensitivity, and high fracture energy (23.6 kJ cm^-2). Notably, the PU-Ene_x demonstrated fast self-healing at room temperature recovering almost 90% of their original toughness within 6 h post-injury. Finally, they also exhibited remarkable adhesive strength (1.0 MPa), high optical transparency and strong blue fluorescence upon UV irradiation. The work demonstrates development of a novel, multifunctional PU with outstanding mechanical properties and enhanced self-healing at ambient conditions, enabling an exciting range of new applications.