Junqi Sun

Abstract Spider silk is one of the most robust natural materials, which has extremely high strength in combination with great toughness and good elasticity. Inspired by spider silk but beyond it, a healable and recyclable supramolecular elastomer, possessing superhigh true stress at break (1.21 GPa) and ultrahigh toughness (390.2 MJ m −3 ), which are, respectively, comparable to and ≈2.4 times higher than those of typical spider silk, is developed. The elastomer has the highest tensile strength (ultimate engineering stress, 75.6 MPa) ever recorded for polymeric elastomers, rendering it the strongest and toughest healable elastomer thus far. The hyper‐robust elastomer exhibits superb crack tolerance with unprecedentedly high fracture energy (215.2 kJ m −2 ) that even exceeds that of metals and alloys, and superhigh elastic restorability allowing dimensional recovery from elongation over 12 times. These extraordinary mechanical performances mainly originate from the meticulously engineered hydrogen‐bonding segments, consisting of multiple acylsemicarbazide and urethane moieties linked with flexible alicyclic hexatomic spacers. Such hydrogen‐bonding segments, incorporated between extensible polymer chains, aggregate to form geometrically confined hydrogen‐bond arrays resembling those in spider silk. The hydrogen‐bond arrays act as firm but reversible crosslinks and sacrificial bonds for enormous energy dissipation, conferring exceptional mechanical robustness, healability, and recyclability on the elastomer.

Heal thyself! Self-healing superhydrophobic coatings are fabricated by preserving healing agents of reacted fluoroalkylsilane in layered polymeric coatings that are porous and rigidly flexible. When the top layer of fluoroalkyl chains decomposes or the coatings are scratched, the healing agents migrate to the surface to restore the superhydrophobicity of the coatings (see picture). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract There is a huge requirement of elastomers for use in tires, seals, and shock absorbers every year worldwide. In view of a sustainable society, the next generation of elastomers is expected to combine outstanding healing, recycling, and damage‐tolerant capacities with high strength, elasticity, and toughness. However, it remains challenging to fabricate such elastomers because the mechanisms for the properties mentioned above are mutually exclusive. Herein, the fabrication of healable, recyclable, and mechanically tough polyurethane (PU) elastomers with outstanding damage tolerance by coordination of multiblock polymers of poly(dimethylsiloxane) (PDMS)/polycaprolactone (PCL) containing hydrogen and coordination bonding motifs with Zn 2+ ions is reported. The organization of bipyridine groups coordinated with Zn 2+ ions, carbamate groups cross‐linked with hydrogen bonds, and crystallized PCL segments generates phase‐separated dynamic hierarchical domains. Serving as rigid nanofillers capable of deformation and disintegration under an external force, the dynamic hierarchical domains can strengthen the elastomers and significantly enhance their toughness and fracture energy. As a result, the elastomers exhibit a tensile strength of ≈52.4 MPa, a toughness of ≈363.8 MJ m −3 , and an exceptional fracture energy of ≈192.9 kJ m −2 . Furthermore, the elastomers can be conveniently healed and recycled to regain their original mechanical properties and integrity under heating.

Flame-retardant and self-healing superhydrophobic coatings are fabricated on cotton fabric by a convenient solution-dipping method, which involves the sequential deposition of a trilayer of branched poly(ethylenimine) (bPEI), ammonium polyphosphate (APP), and fluorinated-decyl polyhedral oligomeric silsesquioxane (F-POSS). When directly exposed to flame, such a trilayer coating generates a porous char layer because of its intumescent effect, successfully giving the coated fabric a self-extinguishing property. Furthermore, the F-POSS embedded in cotton fabric and APP/bPEI coating produces a superhydrophobic surface with a self-healing function. The coating can repetitively and autonomically restore the superhydrophobicity when the superhydrophobicity is damaged. The resulting cotton fabric, which is flame-resistant, waterproof, and self-cleaning, can be easily cleaned by simple water rinsing. Thus, the integration of self-healing superhydrophobicity with flame retardancy provides a practical way to resolve the problem of washing durability of the flame-retardant coatings. The flame-retardant and superhydrophobic fabric can endure more than 1000 cycles of abrasion under a pressure of 44.8 kPa without losing its flame retardancy and self-healing superhydrophobicity, showing potential applications as multifunctional advanced textiles.

The fabrication of highly durable skin-mimicking sensors remains challenging because of the unavoidable fatigue and physical damage that sensors are subjected to in practical applications. In this study, ultra-durable ionic skins (I-skins) with excellent healability and high sensitivity are fabricated by impregnating ionic liquids (ILs) into a mechanically robust poly(urea-urethane) (PU) network. The PU network is composed of crystallized poly(ε-caprolactone) and flexible poly(ethylene glycol) that are dynamically cross-linked with hindered urea bonds and hydrogen bonds. Such a design endows the resultant ionogels with high mechanical strength, good elasticity, Young's modulus similar to that of natural skin, and excellent healability. The ionogel-based I-skins exhibit a high sensitivity to a wide range of strains (0.1-300%) and pressures (0.1-20 kPa). Importantly, the I-skins show a highly reproducible electrical response over 10 000 uninterrupted strain cycles. The sensing performance of the I-skins stored in open air for 200 days is almost the same as that of the freshly prepared I-skin. The fractured I-skins can be easily healed by heating at 65 °C that restores their original ultra-durable sensing performance. The long-term durability of the I-skins is attributed to the combination of non-volatility of the ILs, excellent healability, and well-designed mechanical properties.