Shaping topological structures and intrinsic properties of aramid nanofiber films through fluid flow templating

With the development of nanomaterials and nanotechnologies, aramid nanofibers (ANFs) have gained great popularity in the field of advanced functional nanocomposites owing to their excellent comprehensive performance. The assembly process of nano-structured blocks has a significant impact on the topological architectures and intrinsic properties of the final products. In this work, a fluid flow templating strategy is used to optimize the structure of nano-assembly units and regulate the intrinsic thermally conductive and mechanical properties of the assembled nanomaterials, with emphasis placed on the evolution of assembly units during the proton reduction of ANFs. The hydrodynamic environment during reprotonation acts as an effective template for the self-assembly of ANFs. By tuning the Reynolds number of the fluid, 3 distinct classes of micro-/nano-structures including lamellae, fibers, and dendricolloids are identified. The continuous and dense fibrous network formed at moderate shear rates effectively minimizes phonon scattering and stress concentration, outperforming the void-rich lamellar stacking and heterogeneous dendritic structures. Consequently, the optimized ANF film achieves an exceptional intrinsic thermal conductivity of 5.49 W m^-1 K^-1 and a tensile strength exceeding 200 MPa. This work elucidates the intrinsic relationship between the topological structure and material performance, offering an attractive pathway for designing fiber-assembled thermally conductive polymer films with synchronously enhanced heat transfer and mechanical properties.