Multifunctional\nPolyurethane Networks Combining Strength,\nToughness, and Fast Autonomous Self-Healing via the Synergy of Multiple\nDynamic Bonds

Abstract

Polymeric materials exhibiting concomitant toughness,\nstrength,\nand autonomous self-healing at room temperature are attractive in\nmany applications. However, the mechanical strength often compromises\nthe self-healing capability, making development of such materials\nchallenging. Here, we developed multifunctional supramolecular polyurethane\n(PU) based elastomers of high toughness and fast autonomous self-healing\ncapacity at ambient conditions via the synergy of quadruple H-bonds\nand dynamic boronic ester bonds. The design involves the use of reversible\nquadruple H-bonding ureido-pyrimidinone (UPy) motifs and soft olefin\nside chains to endow the elastomer with toughness and chain flexibility\nto support self-healing. Further cross-linking of the photoreactive\nolefin groups via dynamic boronic ester bonds by thiol-ene chemistry\nprovided strength while maintaining self-healing at ambient conditions.\nThe resulting elastomers (PU-Ene_<i>x</i>) showed\nhigh toughness (42.8 MJ m^–3), strength (11.1 MPa),\nnotch insensitivity, and high fracture energy (23.6 kJ cm^–2). Notably, PU-Ene_<i>x</i> demonstrated fast\nself-healing at room temperature, recovering almost 90% of their original\ntoughness within 6 h postinjury. Finally, they also exhibited remarkable\nadhesive strength (1.0 MPa), high optical transparency, and strong\nblue fluorescence upon UV irradiation. The work demonstrates the development\nof a novel, multifunctional PU with outstanding mechanical properties\nand enhanced self-healing at ambient conditions, enabling an exciting\nrange of new applications.