Room‐Temperature Self‐Healing Soft Composite Network with Unprecedented Crack Propagation Resistance Enabled by a Supramolecular Assembled Lamellar Structure

Abstract Soft self‐healing materials are compelling candidates for stretchable devices because of their excellent compliance, extensibility, and self‐restorability. However, most existing soft self‐healing polymers suffer from crack propagation and irreversible fatigue failure due to easy breakage of their dynamic amorphous, low‐energy polymer networks. Herein, inspired by distinct structure–property relationship of biological tissues, a supramolecular interfacial assembly strategy of preparing soft self‐healing composites with unprecedented crack propagation resistance is proposed by structurally engineering preferentially aligned lamellar structures within a dynamic and superstretchable poly(urea‐ureathane) matrix (which is elongated to 24 750× its original length). Such a design affords a world‐record fracture energy (501.6 kJ m −2 ), ultrahigh fatigue threshold (4064.1 J m −2 ), and outstanding elastic restorability (dimensional recovery from 13 times elongation), and preserving low modulus (1.2 MPa), high stretchability (3200%), and high room‐temperature self‐healing efficiency (97%). Thereby, the resultant composite represents the best of its kind and even surpasses most biological tissues. The lamellar 2D transition‐metal carbide/carbonitride (MXene) structure also leads to a relatively high in‐plane thermal conductivity, enabling composites as stretchable thermoconductive skins applied in joints of robotics to thermal dissipation. The present work illustrates a viable approach how autonomous self‐healing, crack tolerance, and fatigue resistance can be merged in future material design.