Fast self-healing engineered by UV-curable polyurethane contained Diels-Alder structure

From Slow to Fast Self-Healing at Ambient Temperature of High-Modulus Reversible Poly(methacrylate) Networks. Single- and Dual-Dynamics and the Effect of Phase Separation

“…The majority of intrinsically self-healing studies on reversible covalent polymer networks focus on low-modulus materials in the elastomeric state. This means that the sealing and healing stages are performed at temperatures ( T app ) higher than the material’s glass-transition temperature ( T g ) in homogeneous systems or higher than the T g of the major phase (matrix phase) in phase-separated systems at which the (homogeneous or phase-separated) polymer network exhibits sufficient segmental mobility ( T app > T g ). − Self-healing studies around or below the network’s T g are scarce. Extrinsic self-healing of thermosets at room temperature is described by embedding mobile (dissolved) self-healing agents in microcapsules , Also, few studies can be found on intrinsically self-healing polymer networks at temperatures below the T g in the (partially) vitrified state under high-modulus conditions ( T app < T g ). − However, this is very relevant for protective coatings in both indoor and outdoor applications with a certain operation temperature window around the ambient temperature.…”

“…Supramolecular hydrogen bonding is an excellent tool to facilitate self-healing and is used in support of reversible Diels–Alder chemistry to design dynamic self-healing networks based on a dual (hybrid) self-healing mechanism. The mechanical properties of dynamic polymer networks containing Diels–Alder crosslinks may generally be improved by introducing hydrogen bonds as supramolecular crosslinks. ,,− …”

Preparation and Properties of Self-Healing Polyurethane Elastomer Derived from Tung-Oil-Based Polyphenol

“…For this reason, self-healing polyurethanes become a new development trend due to the internal ability to restore physical failures and microcracks . Self-healable polyurethanes can be produced through dynamic covalent bonding (e.g., Diels–Alder (DA) or retro-DA reaction, − esterifcation, disulfide bonds, − acylhydrazone bond, alkoxyamine chemistry, transcarbamoylation, , nitroxides , ) or noncovalent bonding (e.g., H 2 bonding, π–π stacking, metal-ion binding). The noncovalent method based on hydrogen bonding or metal–ligand linking can heal a polymer repeatedly but largely weakens the noncovalent connection.…”

“…However, the reverse reaction temperature of most DA reactions is very high, and many reverse reactions can only produce stable aromatic compounds instead of dienes or dienophiles . This is why self-healable polyurethane research on DA reactions is mostly limited to the reversible DA reactions between maleimide and furan. − The self-repair capability of polymers is particularly attributed to these reversible covalent bonds, which must be incorporated to polymers in the above self-healing systems. Enthetic groups are essentially important in such a complicated process.…”

Recent Progress in Self‐healing Materials for Sensor Arrays

“…This is typically accomplished by physical interaction or chemical interaction, as sketched in Figure 1. Most intrinsic recovery designs rely upon either reversible covalent bonds, such as Diels‐Alder reactions, [2–12] disulfide bonds, [13–17] boronate ester bonds, [18–21] and imine bonds, [22–24] or non‐covalent, including hydrogen bonds, [25–32] ionic, [33–37] and hydrophobic interactions, [38–40] host‐guest interactions, [41–45] π‐π stacking, [46–48] and metal coordination [49–54] or supramolecular chemistry.…”