Benign integrated synthesis–casting of transparent aramid films with superior dielectric and mechanical properties

Aramid films are widely used as high-performance dielectric and structural materials, yet conventional fabrication from Kevlar fibrils requires prolonged dispersion in concentrated acids, leading to non-uniformity, opacity, and degraded mechanical properties. In this study, we report a benign integrated synthesis–casting process that directly links aramid copolymer synthesis in organic solvents to film fabrication via bar coating, eliminating the need for sulfuric acid dissolution and fibril dispersion. The resulting films exhibit uniform thickness in the range of only a few micrometers, while maintaining high optical transparency, smooth nanoscale surface morphology, and superior mechanical robustness. They also demonstrate exceptional dielectric strength (∼650 kV/mm), outstanding thermal stability, and excellent tensile performance even at such reduced thickness. Furthermore, the films enabled reliable operation as ultrathin gate dielectrics in organic thin-film transistors. These results highlight a scalable and environmentally safer strategy for producing high-performance aramid films ideally suited for advanced applications in flexible electronics, energy storage, and separation technologies. • A benign synthesis-casting process was developed to produce transparent aramid films without sulfuric acid or fibril dispersion. • The films exhibit micrometer-scale thickness, high transparency, and dielectric strength (∼650 kV/mm) with superior stability. • This approach offers a scalable, environmentally benign route for high-performance aramid dielectrics in flexible and energy devices.