Aromatic polyimine covalent adaptable networks with superior water and heat resistances

Polyimine covalent adaptable networks (CANs) exhibit several dynamic characteristics (such as recyclability and reprocessability) that are beneficial for compensating for the disadvantages of traditional petroleum-based synthetic thermosetting resins, and are therefore suggested as potential substitutes for environmentally unfriendly resins. However, owing to the lack of sufficient stability of imine bonds and their linked molecular chains, most polyimine CANs do not exhibit superior properties in applications with high stability requirements, such as strong water resistance, high heat resistance, and excellent mechanical strength. In this study, we designed and synthesized a new class of aromatic petroleum-based polyimine CANs to improve the stability of imine bonds and molecular chains employing the conjugation effect of the two benzene rings to C=N and aromatic structures. In contrast, these CANs simultaneously demonstrate superior water resistance (water absorption: 0.14–0.15%) and heat resistance (5% weight loss (Td5%): 434–441 °C; glass transition temperature (Tg): 217–239 °C) than that of previously reported polyimine CANs (water absorption: 0.90–90%; Td5%: 200–348 °C; Tg: 47–215 °C). They have outstanding mechanical properties that are almost unaffected by adsorbed water. Meanwhile, the resins exhibited remarkable resistance to ordinary acids, bases, oxidants, salts, solvents, and oils, except for several special solvents. In addition, like other polyimine CANs, they maintain their dynamic behavior characteristics, including degradability, recyclability, malleability, reprocessability, and rehealability. This study provides a new method to improve the comprehensive performance of polyimine CANs through reasonable molecular structure design.