Autonomous Underwater Self‐Healable Adhesive Elastomers Enabled by Dynamical Hydrophobic Phase‐Separated Microdomains

Abstract High‐efficient underwater self‐healing materials with reliable mechanical attributes hold great promise for applications in ocean explorations and diverse underwater operations. Nevertheless, achieving these functions in aquatic environments is challenging because the recombination of dynamic interactions will suffer from resistance to interfacial water molecules. Herein, an ultra‐robust and all‐environment stable self‐healable polyurethane‐amide supramolecular elastomer is developed through rational engineering of hydrophobic domains and multistrength hydrogen bonding interactions to provide mechanical and healing compatibility as well as efficient suppression of water ingress. The coupling of hydrophobic chains and hierarchical hydrogen bonds within a multiphase matrix self‐assemble to generate dynamical hydrophobic hard‐phase microdomains, which synergistically realize high stretchability (1601%), extreme toughness (87.1 MJ m −3 ), and outstanding capability to autonomous self‐healing in various harsh aqueous conditions with an efficiency of 58% and healed strength of 12.7 MPa underwater. Furthermore, the self‐aggregation of hydrophobic clusters with sufficient dynamic interactions endows the resultant elastomer with effective instantaneous adhesion (6.2 MPa, 941.9 N m −1 ) in extremely harsh aqueous conditions. It is revealed that the dynamical hydrophobic hard‐phase microdomain composed of hydrophobic barriers and cooperative reversible interactions allows for regulating its mechanical enhancement and underwater self‐healing efficiency, enabling the elastomers as intelligent sealing devices in marine applications.