Healable, Recyclable,\nand Ultra-Tough Waterborne Polyurethane\nElastomer Achieved through High-Density Hydrogen Bonding Cross-Linking\nStrategy

With the increasing popularity of elastomers in industry\nand daily\nlife, their high performance and functionality have attracted widespread\nattention. However, it is a great challenge for them to possess both\nhigh mechanical properties and excellent healing and recovery capabilities\ndue to the limitations of the preparation methods and the intrinsic\nmicrostructure of the elastomers. In this study, a strategy of ice-controlled\ninterfacial stepwise cross-linking was proposed to prepare the waterborne\npolyurethane-based elastomers with ultrahigh-density hydrogen bonding\ninteraction achieved by enhancing the utilization rate of phenol hydroxyl\ngroups of tannic acid to the maximum extent. The elastomers have incredible\nmechanical properties, including ultrahigh toughness of 1.03 GJ m<sup>–3</sup> (which represents the highest level among polyurethane\nelastomers prepared through common processing techniques to date),\nextremely high true fracture stress of ∼1.9 GPa, world-record\nfracture energy of 520 kJ m<sup>–2</sup>, and exciting multiple\nfunctional characteristics, such as highly efficient self-healing\nability of 10 min, high resistance to physical damage and chemical\ncorrosion, broad temperature and frequency damping effects, good shape\nmemory effect, and excellent melt-processing recyclability and solvent\nrecyclability. These robust multifunctional elastomers represent considerable\npotential in various fields, from defense and military industry and\ncivil transportation to precision manufacturing, etc.