Enhanced Dielectric Constant, Ultralow Dielectric Loss, and High-Strength Imide-Functionalized Graphene Oxide/Hyperbranched Polyimide Nanocomposites

We achieved for the first time the formation of a charge-transfer complex (CTC) between a novel hyperbranched polyimide (PI) and oligo-imide-functionalized graphene oxide (FGO), aiming for enhancing the dielectric properties of resulting PI–FGO nanocomposites. This novel hyperbranched PI was derived from a new diamine <i>N</i>¹,<i>N</i>¹′-(4,4′-oxybis­(4,1-phenylene))­bis­(<i>N</i>¹-(4-aminophenyl)­benzene-1,4-diamine). The imide moieties were integrated on amine-FGO via a step-by-step condensation and thermal imidization approach. This FGO exhibited excellent compatibility with hyperbranched PI because of the formation of a CTC between two domains. In viscoelastic measurements, the dynamic storage modulus and glass-transition temperature of flexible PI–FGO nanocomposites increased linearly with increasing FGO contents. The synthesized nanocomposites revealed high mechanical properties with a tensile strength as high as 1.122 GPa. Thermogravimetric analysis demonstrates that these nanocomposite films exhibit high thermal stability up to 550 °C. Remarkably, the dielectric constant increases up to 42.47 at 8 wt % FGO loading with a dielectric loss as low as 0.0018 while maintaining the breakdown strength as high as 147.3 ± 4.5 MV/m