Self-healing and recyclable polymer materials are being developed through extensive investigations on noncovalent bond interactions. However, they typically exhibit inferior mechanical properties. Therefore, the present study is aimed at synthesizing a polyurethane–urea elastomer with excellent mechanical properties and shape-memory-assisted self-healing behavior. In particular, the introduction of coordination and hydrogen bonds into elastomer leads to the optimal elastomer exhibiting good mechanical properties (strength, 76.37 MPa; elongation at break, 839.10%; toughness, 308.63 MJ m⁻³) owing to the phased energy dissipation mechanism involving various supramolecular interactions. The elastomer also demonstrates shape-memory properties, whereby the shape recovery force that brings damaged surfaces closer and facilitates self-healing. Surprisingly, all specimens exhibite clustering-triggered emission, with cyan fluorescence is observed under ultraviolet light. The strategy reported herein for developing multifunctional materials with good mechanical properties can be leveraged to yield stimulus-responsive polymers and smart seals.

The mechanism of enhancing the mechanical and tribological properties of polytetrafluoroethylene (PTFE) via the addition of nano-ZrO₂ was investigated by virtue of molecular dynamic (MD) simulation from an atomic level. The MD was used to explore stretch and break of molecular chains for understanding the inherent mechanism of nanocomposites. The results found that elastic modulus of PTFE and PTFE/ZrO₂ were 1.42 GPa and 6.43 GPa, respectively. The average friction coefficients of PTFE and PTFE/ZrO₂ were 0.168 and 0.113, respectively. Compared to PTFE, the friction coefficient of PTFE/ZrO₂ decreased by 32.7%. To explore the microscopic friction mechanism, the radial distribution function, atomic concentration, and atomic velocity were simulated and interpreted accordingly during the tribological process.

Over the past two decades, covalent organic frameworks (COFs) have become the most widely studied porous crystalline materials. Their specific physical and chemical properties are determined by the arrangement of atoms (crystal structure). Therefore, the determination of their structure is arguably the most important characterization step for COFs. Although single-crystal X-ray diffraction is the most widely used method for structure determination, confirmation of the structure of COFs is limited to lattice fringes in transmission electron microscopy (TEM) because of their small crystal size (nanocrystals) or poor crystal quality. At present, many two-dimensional COFs (2D-COFs) have clear powder X-ray diffraction (PXRD) patterns, but specific lattice fringes are not available for all 2D-COFs. This severely hinders the development of the COF field. Here, we discovered the lattice shrinkage behavior of COFs under electron beam irradiation by comparing the lattice fringes of 2D-COFs under different conditions. By comparing the lattice fringes of a 1,3,5-tris-(4-aminophenyl)triazine-1,3,5-tris-(4-formylphenyl)triazine covalent organic framework (TAPT-TFPT COF) at room temperature and under liquid nitrogen freezing conditions, we found that the lattice fringes are in good agreement with the PXRD and the theoretical values of the COF (2.213 nm) under freezing conditions. However, the lattice fringe spacing is only 1.656 nm at room temperature. The discovery not only provides new insights into the TEM characterization of COFs, but also further expands the range of crystalline COF materials.

Recyclability of thermosetting polymers and their composites is a challenge for alleviating environmental pollution and resource waste. In this study, solvent-recyclable thermosetting polyimide (PI) and its composite were successfully synthesized. The tensile strength, elongation at break, and Young’s modulus of PI are 108.70 ± 7.29 MPa, 19.35% ± 3.89%, and 2336.42 ± 128.00 MPa, respectively. The addition of reduced graphene oxide (RGO) not only enhances the mechanical properties of PI but also endows it with excellent tribological properties. The PI illustrates a high recycling efficiency of 94.15%, but the recycled composite exhibits inferior mechanical properties. The recycling and utilization of PI and its composite are realized through imine bonds (–C=N), which provides new guidance for solving the problem of environmental pollution and resource waste and is potential application in the field of sustainable tribology.