Balancing Mechanical Performance and Self‐Healing in Polyurethanes via Hard Segment‐Tuned Dual Dynamic Networks

ABSTRACT Conventional polyurethane materials often suffer from irreversible mechanical damage and limited durability, which restrict their service life and reliability in demanding applications. To address this limitation, this study developed a series of self‐healing polyurethanes (SHPUs) by incorporating dual dynamic covalent bonds, thiourethane linkages, and disulfide bonds into a hydroxyl‐terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) matrix. By tuning the hard segment (HS) content from 15 to 30 wt%, the materials' mechanical and self‐healing performance were systematically investigated through the synergism of thiourethane and disulfide bonds, which enable efficient self‐repair without compromising structural integrity. Mechanical analysis showed that increasing HS content enhanced tensile strength and modulus, with SHPU‐30 exhibiting the highest tensile properties. However, SHPU‐25 achieved the optimal balance between stiffness and healing, attaining over 90% healing efficiency after 12 h at 60°C. FTIR and Raman spectroscopy confirmed the successful incorporation of the dynamic bonds. Temperature‐dependent studies further revealed accelerated healing at elevated temperatures, with near‐complete recovery achieved at 70°C. These results demonstrate the effectiveness of dual dynamic bonding in enabling robust, thermally triggered self‐healing behavior, making these SHPUs promising candidates for advanced coatings, elastomers, and functional materials with extended service life.