Intermolecular hydrogen bonding enabling mechanically robust, thermally stable, and solvent-resistance bio-based polyimine networks

With the increasing awareness of environmental protection and the concept of sustainable development, covalent adaptable networks are receiving growing attention due to their intelligent functionalities and sustainability. However, they still face challenges, including how to balance comprehensive performance, dynamic features and high flammability. Herein, lignin-derived vanillin was used as a precursor to synthesize the bio-based polyimine (TMP-IPDA-Si) with excellent comprehensive performance and certain fire safety properties. The molecular dynamics simulations showed that the introduction of hydrazide structures and the formed acylhydrazone bonds enhanced the intermolecular hydrogen bonding interactions between the polymer networks, resulting in polyimine materials with outstanding mechanical properties (tensile strength of 85.7 MPa) and high T_g (201.4 °C). The TMP-IPDA-Si exhibited excellent solvent resistance, retaining over 90 % of its mechanical properties after 72 h in aqueous solutions. It also showed outstanding thermal stability and high char yield (over 46 %), surpassing many previously reported polyimine. In MCC tests, the TMP-IPDA-Si displayed low THR (8.5 kJ g⁻¹) and PHRR (170.5 W g⁻¹) value. This study lays the scientific groundwork for designing bio-based polyimines with superior mechanical properties and high T_g, offering potential for broader applications in fire-safe and sustainable materials.