Orientation-engineered polymer dielectrics with ultralow nanofiller loading for suppressed dielectric loss and enhanced mechanical robustness

The demand for higher integration and operational stability in modern electronics has increased the need for polymers with excellent dielectric and mechanical properties. While incorporating nanofillers can enhance dielectric performance, high loadings often worsen mechanical properties and dielectric loss. Achieving low dielectric loss and high mechanical robustness under ultralow nanofiller loadings remains a critical yet unsolved challenge. Here, we present polypropylene (PP) nanocomposites with only 0.5 wt.% nanofillers, fabricated via a combination of stretching orientation and annealing strategies. The coupled orientation of molecular chains and nanofillers under stretching generates a spatially ordered dielectric framework that increases crystallinity by ~ 10% and mitigates electric field concentration. Subsequent annealing stabilizes this oriented structure through constrained chain relaxation and crystalline perfection, reducing losses during dipole steering. The optimal nanocomposites exhibit remarkable breakdown strength (528 MV/m) and tensile strength (215 MPa), while maintaining ultralow dielectric loss (5.5 × 10⁻⁴), outperforming most PP-based composites. Finite element simulations indicate that the homogeneous and directional arrangement of nanofillers effectively hinders electrical damage propagation. Additionally, the oriented nanocomposites demonstrate exceptional impedance matching, which is beneficial for signal transmission. This strategy addresses the trade-off between enhanced insulation and low filler loading, enabling polymer nanocomposites with efficient signal transmission and reliable processability.