Dual Deprotonation‐Enabled 3D Hydrogen‐Bonding Networks in Aramid Nanofiber Films Toward Extraordinary Mechanical Strength and Ultralow Thermal Conductivity

Developing thin materials that simultaneously exhibit high mechanical strength and low thermal conductivity is fundamentally challenging due to the intrinsic trade‐off between structural reinforcement and thermal insulation. Herein, a dual deprotonation strategy is presented to create robust, layered aramid nanofiber films with low thermal conductivity. The pure organic composite films possess a tensile strength of 202.5 MPa, toughness of 24.1 MJ m−3, and thermal conductivity of 0.0824 W m−1K−1, coupled with excellent thermal stability (decomposition temperature: 415.4 °C) and water resistance. Notably, these films retain over 95% of their mechanical strength across a broad temperature range (from −30 to 150 °C), surpassing intrinsic aramid nanofiber films, which maintain only 68% under similar conditions. This exceptional performance arises from strong interfacial 3D hydrogen‐bonding networks, enabling efficient load transfer and thermal regulation between nanofibers and surface polymers. The findings offer a design strategy for next‐generation lightweight materials that unify robust mechanical properties and thermal insulation or other properties, thus expanding their applicability in specific environments.