Two diepoxides containing a two-benzene-ring-conjugated Schiff base when cured with an aromatic diamine result in high-performance thermosets combining excellent controlled degradability, stability and antibacterial properties. Epoxy resins have been widely used in coatings, adhesives, composites, electronic packaging materials, etc., but they are arduous to recycle and have no antibacterial activity. In this paper, two-benzene-ring-conjugated Schiff base diepoxy monomers were synthesized and further cross-linked with 4,4-diaminodiphenylmethane. The chemical structures of the diepoxides as well as their thermosets were characterized in detail. The property investigation manifested that the thermosets possessed a far higher glass transition temperature of ∼206 °C, tensile strength of ∼122 MPa, and tensile modulus of ∼2646 MPa than a commonly used high-performance bisphenol A epoxy resin. Moreover, they possessed excellent acidity and temperature-controlled degradability, and superior stability in common solvents, thermal treatment and hygrothermal aging. Furthermore, they presented excellent coating properties (including hardness, adhesion, and solvent resistance) and antibacterial properties with a bactericidal capability of ∼91%.

Covalent adaptable networks (CANs) provide a promising approach to solve the issue of recycling thermosets due to their dynamic cross-linked networks. However, CANs are susceptible to creep at relatively low temperatures, and their chemical stability is also inevitably doubtful. Here, we designed novel dihydrazone CANs by cross-linking a dihydrazone-containing epoxy monomer, which was synthesized from the condensation of a lignin derivative vanillin and hydrazinium hydrate, followed by a reaction with epichlorohydrin. Besides the excellent malleability and reprocessability, the dihydrazone CANs exhibited a high initial creep temperature of ∼105 °C, which was ascribed to the superior stability of the hydrazone bond at around 100 °C and favorable hydrazone exchangeability at elevated temperatures. Meanwhile, the degradation of the dihydrazone CANs exhibited temperature, solvent, and acidity dependence. Moreover, on account of the high antibacterial properties of the hydrazone bond, the CANs presented a high killing rate (95.8%) for Gram-negative bacteria (E. coli). Thus, this work discloses an effective dynamic covalent motif for the development of CANs with excellent dimensional stability, chemical resistance, and intrinsic antibacterial properties.