Mechanically Robust and Highly Transparent Polyurethane Elastomer With Excellent Adhesion Enabled by Hierarchical Hydrogen Bonds

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ABSTRACT Many high‐strength polyurethane materials have been developed in the past, but combining other functionalities such as high transparency, adhesion, and self‐healing properties is still a great challenge. We prepare a mechanically robust polyurethane elastomer with high transparency and self‐healability. The relationship between its structure and properties is elaborated. Acylsemicarbazide (ASCZ) and urethane groups are introduced into the hard segments of the polyurethane elastomer, and by modulating the spacer groups between the ASCZ and urethane groups, the fine modulation for the hydrogen bonding density and the hard domain size is realized. By the exquisite regulation of molecular structure, the HMDI‐SPH elastomer with sebacic dihydrazide (SPH) as the chain extender, polytetramethylene ether glycol (PTMEG) as the soft segments, and methylene‐bis(4‐cyclohexyl isocyanate) (HMDI) as the isocyanate can achieve a high elasticity due to the rich and hierarchical hydrogen bonds. Such hydrogen bonds impede the crystallization of PTMEG and facilitate the formation of homogeneously distributed hard‐phase microdomains. The HMDI‐SPH elastomer exhibits good mechanical robustness (tensile strength of 45.7 MPa, toughness of ~140.8 MJ m −3 ), transparency (transmittance > 95%), and self‐healing (self‐healing efficiency of 86.6%). Meanwhile, HMDI‐SPH has good adhesive strength on a variety of substrates such as walnut (~10.81 MPa) and steel (~14.60 MPa).

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