Stable mechanical properties under cyclic mechanical loads are critical for the applications of hydrogels in flexible electronics and tissue engineering. However, most existing tough hydrogels still face obvious notch sensitivity and suffer from fatigue fracture under continuous load. Designing hydrogels with multifunctional properties, such as high stretchability, toughness, and excellent antifatigue fracture, through a facile strategy is on demand. In this work, the nanocomposite hydrogels with comprehensive mechanical properties were prepared by one-pot polymerization of acrylamide (AM), isocyanoethyl methacrylate-glutamine (IEM-Gln), and Laponite XLG nanosheets. Owing to the potent hydrogen bonds formed by urea groups in IEM-Gln and hydrogen-bonding interaction between the polymer chain and nanoclays, the presented nanocomposite hydrogels displayed excellent mechanical properties (tensile strength of 160 kPa, stretchability of 2600%, compressive strength of 2.3 MPa, and toughness of 3300 J/m2). It was noteworthy that the hydrogels exhibited excellent notch insensitivity and fatigue fracture resistance, and even after 50 cycles, there was no measurable crack propagation observed. In addition, the introduction of clay nanosheets into the gelation system endowed the composite hydrogels with outstanding hemostatic activity and tissue adhesiveness. The nanocomposite hydrogels could not only reduce the skin tension of the wound tissue by their high tensile properties but also accelerate hemostasis in the first stage of wound healing, both of which led to the fast healing of skin wound in mice.

Development of hydrogel-based flexible electronics with robust elasticity, low hysteresis, and excellent durability is still challenging. Herein, for the first time, B–N coordination was employed as the main driving force to promote gelation by free radical polymerization of acrylamide and 3-acrylamidophenylboronic acid. Owing to the outstanding stability of B–N coordination, the hydrogels could retain their initial stress (>95%) during 500 tension cycles (strain of 200%) with <10% hysteresis. Moreover, the addition of NaCl elevated the mechanical properties (break stress of 0.21 MPa and fracture strain of 1600%) and imparted high electrical conductivity (4.8 S/m) and superior gauge factor (10.2) to the hydrogels. The conductive hydrogels could accurately distinguish various deformations (2.5–200% tensile strain and 1–25 kPa compressive stress) and successively output reliable electrical signals with super durability (1000 tensile cycles with a strain of 100% and 1000 compressive cycles with a stress of 15 kPa). Combined with moderate tissue adhesiveness, the conductive hydrogels can monitor various human activities with constant outputs. This work offers a new solution to integrate high stretchability, robust elasticity, and low hysteresis into noncovalent cross-linked hydrogels, and may show vast potential in the development of flexible electronic devices.

Phosphorus-doped hollow carbon nanorods with high electronic conductivity can maintain excellent structural stability and endow outstanding electrochemical performance in sodium-based dual-ion batteries.

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