A continued nano-carbon network endowing the polyvinyl alcohol composite films with super-high electrical and thermal conductivity

To address key trade-offs in carbon-based composites—conductivity vs. dispersibility, flexibility vs. high filler loading—a double-filled polyvinyl alcohol composite (PVAC) film was developed. Integrate sodium hypochlorite-oxidized multi-walled carbon nanotubes (O-MWCNTs) and reduced graphene oxide (rGO) into a PVA matrix via vacuum-induced self-assembly and thermal-pressure lamination. A green hypochlorous acid oxidation strategy endows O-MWCNT with GO-like water dispersibility while preserving reducibility, overcoming the dispersion-conductivity trade-off. Oxygen functional groups on O-MWCNTs enhance dispersion and act as dynamic anchors for PVA chains, promoting long-range polymer interlinking (rather than confinement) to maintain flexibility—retaining over 96 % thermal conductivity (k) after 1000 folding cycles. Scanning electron microscopy confirmed the formation of continuous 3D nano-carbon networks, where O-MWCNTs act as vertical interconnects bridging the rGO nanosheets, establishing continuous conductive and heat conduction pathways. PVA chains form an elastic “web” around functionalized fillers, with hydrogen bonds between hydroxyl groups (-OH) of PVA and oxygen moieties (-COOH, -C=O) on nanocarbons enabling stress redistribution. At a rGO:O-MWCNT ratio (4:6) and 70 wt% filler loading, the films exhibit superhigh in-plane/through-plane electrical (3007.5/721.5 S/m) and thermal (67.7/11.5 W/m·K) conductivities. Notably, they maintain ∼7.8 % elongation at break, defying the rigidity-conductivity trade-off, thanks to oxygen-mediated interfaces where sacrificial hydrogen bonds dissipate strain while preserving conductive networks. This dual-filler design leverages rGO (lateral conduction) and O-MWCNTs (vertical bridges) to overcome conductivity anisotropy. The films' exceptional electrical-thermal-mechanical performance, paired with scalable fabrication, positions them as a transformative platform for flexible electronics, thermal interface materials, and energy storage systems.