Breaking the strength-toughness trade-off in high-performance polyimide nanocomposites using solution-processable aminated heterocyclic polyamide-grafted graphene oxide at ultralow loading

Despite extensive research on graphene oxide (GO) functionalization with small molecules, oligomers and flexible-chain polymers, grafting rigid-chain polymers onto GO remains largely unexplored. Conventional GO modifications enhance the strength of polyimide (PI) while compromising ductility. Herein, we synthesized a novel aminated heterocyclic aromatic polyamide (NH 2 -HAP) and covalently grafted it onto GO via carbodiimide coupling, achieving a high grafting ratio of ∼ 37 wt%. Incorporating NH 2 -HAP-grafted GO (GO-g-NH 2 -HAP) into PI through in-situ polymerization, doctor-blading, and then thermal imidization yields nanocomposites with excellent strength, toughness, moisture resistance, and dielectric performance. Amino and imidazole groups in GO-g-NH 2 -HAP promote its uniform dispersion and form strong covalent bonds at the interface, facilitating efficient load transfer. At an ultralow loading of 0.40 wt% GO-g-NH 2 -HAP (∼0.25 wt% GO), the nanocomposite achieves remarkable enhancements in tensile strength (254.1 ± 11.7 MPa, +201 %), modulus (1.70 ± 0.05 GPa, +83 %), elongation at break (54.5 ± 2.4 %, +106 %), and tensile toughness (103.2 ± 6.9 MJ/m 3 , +470 %), overcoming the typical strength-toughness conflict in small-molecule-modified GO/PI nanocomposites. The film also demonstrates an 81 % reduction in water vapor transmission rate, an 88 % decrease in water absorption, and a lower dielectric constant (2.5 vs. 3.2 for neat PI). These exceptional properties make the nanocomposites promising for microelectronics and flexible devices.