Mechanically Robust and Self-Healing Polyurethane Elastomer Based on Hierarchical Hydrogen Bonds

Abstract

It is a formidable challenge to fabricate mechanically robust and self-healing polymeric materials. In this work, a facile but effective approach based on constructing hierarchical hydrogen bonds (H-bonds) is used to combine high mechanical robustness and healing efficiency into one artificial polyurethane (PU) elastomer. The infrared spectrum and molecular simulations demonstrate the formation of hierarchical H-bonds, which are assembled by the strong and weak H-bonds. The hierarchical H-bonds appear to have two advantages. On the one hand, the hierarchical breaking of the strong and weak H-bonds can effectively strengthen and toughen the PU elastomer. The strong H-bonds maintain the integrity of the PU network, while the weak H-bonds dissipate considerable energy during stretching; on the other hand, the rapid dissociation and organization of hierarchical H-bonds provides the driving force for the healing process. Thus, the hierarchical H-bonds efficiently solve the inherent contradiction between mechanical strength and healing dynamics. As a result, the PU elastomer exhibits excellent mechanical properties (32.5 MPa of tensile strength and 84.1 MJ m−3 of toughness). Meanwhile, this PU elastomer shows high healing efficiency (91.4%) and also exhibits 100% scratch recovery. This design strategy may provide a simple yet effective way to produce robust self-healing polymeric materials.