Most tough hydrogels are reinforced by introducing energy dissipation mechanisms, but simultaneously realizing a high toughness and low hysteresis is challenging because the energy dissipation structure cannot recover rapidly. In this work, high mechanical performance highly entangled double network hydrogels without energy dissipation structure are fabricated, in which physical entanglements act as the primary effective crosslinking in the first network. This sliding entanglement structure allows the hydrogel network to form a highly uniform oriented structure during stretching, resulting in a high tensile strength of ~3 MPa, a fracture energy of 8340 J m⁻² and a strain-stiffening capability of 47.5 in 90% water content. Moreover, almost 100% reversibility is obtained in this hydrogel via energy storage based on entropy loss. The highly entangled double network structure not only overcomes the typical trade-off between the high toughness and low hysteresis of hydrogels, but more importantly, it provides an insight into the application of entanglement structures in high-performance hydrogels.

Sub-micrometer hybrid spheres with a poly-dopamine core and loaded with silver nanoparticles (NPs) were fabricated by a facile method. The new hybrid spheres show a strong antibacterial activity due to their special structure, effectively preventing silver NP aggregation.

New linear polyurethane was synthesized via a Diels–Alder (DA) reaction between a polyurethane prepolymer end-capped with furan groups (MPF) and bismaleimide (BMI). The structure of the linear polyurethane with DA bonds was characterized by ¹H NMR, ATI-FTIR, TGA and AFM. The introduction of DA bonds enables the polyurethane thermal reversibility, which was studied thoroughly by ¹H NMR, DSC and GPC. Besides, the new linear polyurethane with DA bonds also exhibits self-healing properties under heat treatment, which was observed by polarized optical microscope. The self-healing efficiency determined by the recovery of breaking tensile strength after being damaged and healed can reach up to 80%.

Primary mono-amine (furfuryl amine) is functionalized as a chain extender to obtain linear polyurethane bearing pendant furan groups (L-PU-Furan), unlike the previous research (furanic diols as chain extender). Furfuryl amine can functionalize as a chain extender due to the reactivity between the resultant urea group and NCO group at higher temperatures. Pendant cross-linked polyurethane containing a DA bond (C-PU-DA) is obtained from the cross-linking of L-PU-Furan and a bismaleimide (BMI) via a Diels–Alder reaction. L-PU-Furan and C-PU-DA are characterized by ¹H NMR, FTIR, DSC and TGA. The results of ¹H NMR and gel–solution–gel experiments demonstrate that the C-PU-DA exhibits excellent thermal reversibility. C-PU-DA exhibits good healable properties as evidenced by the evolution of a crack versus temperature observed under polarizing optical microscopy. C-PU-DA exhibits good mechanical properties and healing efficiency, determined by breaking (tensile) strength measurements.