Dynamic matrix and interfacial Diels-Alder bonding endows graphene oxide/polyurethane nanocomposites with self-healing, mechanical robustness, and enhanced hydrogen barrier performance

Hydrogen barrier materials capable of retaining effective barrier performance after mechanical damage are highly desirable for hydrogen storage and transportation applications. Here, we report a functionalized graphene oxide reinforced polyurethane nanocomposite containing Diels-Alder (DA) bonds, denoted as fGO/PU-DA, in which dynamic DA linkages were incorporated into both the polymer matrix and the nanofiller-matrix interface. The 5 wt% fGO/PU-DA nanocomposite achieved a tensile strength of 9.8 MPa, corresponding to a 75% increase over neat PU-DA, while maintaining a favorable balance between strength and ductility. After cut-healing treatment, the nanocomposite recovered nearly all of its tensile strength, whereas its elongation at break and toughness exceeded their original values even after three damage-healing cycles, highlighting the contribution of interfacial DA bonds to healing efficiency. The hydrogen permeability coefficient decreased from 2.4 × 10 −12 for neat PU-DA to 8.6 × 10 −13  cm 3  cm cm −2 ·s −1  Pa −1 for the 5 wt% fGO/PU-DA nanocomposite, corresponding to a reduction of 64%. Even in the healed state, the permeability remained markedly lower than that of healed PU-DA, indicating a clear barrier advantage after macroscopic damage. Mechanistic analysis indicated that the enhanced barrier performance was diffusion-dominated and originated from interfacial confinement together with reduced cooperative segmental mobility. The material was further validated as a coating on polyamide 6 substrates, where the fGO/PU-DA layer also delivered improved hydrogen barrier performance. These results demonstrate that coupling matrix-level reversible reconstruction with interfacial dynamic DA bonding provides an effective route to polyurethane nanocomposites integrating self-healing capability, mechanical robustness, and superior hydrogen barrier performance.