Kinetically moderated reprotonation reconstructs aramid nanofiber hydrogen-bond networks for high-performance thermal management and EMI shielding composite films

Flexible electronic devices urgently require lightweight multifunctional films that can dissipate heat, suppress electromagnetic interference (EMI), and retain mechanical reliability under repeated deformation. However, filler-rich polymer composites often improve thermal/electrical transport at the expense of matrix integrity, creating a persistent trade-off between thermal conductivity and mechanical robustness. Herein, we report a kinetically moderated reprotonation strategy that shifts the design principle from filler-dominated transport enhancement to time-scale-controlled reconstruction of the aramid nanofiber (ANF) matrix. The acetic acid/ethanol (AE) route couples moderate acid-assisted amide proton recovery with subsequent solvent exchange and nanofiber rearrangement before complete network consolidation. This controlled sequence enables progressive restoration of hydrogen bonding (N–H···O = C) and formation of a dense, ordered ANF-AE nanofibrillar framework. Consequently, the pure ANF-AE film achieves an in-plane thermal conductivity (λ∥) of 7.7 W·m–1·K–1 and a tensile strength of 220 MPa, corresponding to a 133% increase in λ∥ compared with water-reprotonated ANF. After incorporating PDA-functionalized graphene nanoplatelets (fGNP) further strengthens the reconstructed network through hydrogen-bonding and π–π interfacial interactions. The optimized fGNP50/ANF-AE composite film achieves a λ∥ of 81 W·m–1·K–1, EMI shielding effectiveness of 57 dB at 60 μm, tensile strength of 368 MPa, and toughness of 20 MJ‧m− 3. Moreover, the composite retains approximately 95% of its initial properties after 10,000 folding cycles and exhibits excellent thermal stability. This work demonstrates that kinetically moderated ANF reconstruction combined with non-covalent graphene interfacial engineering offers an effective route toward multifunctional composite films for advanced flexible electronics. Kinetically moderated AE reprotonation reconstructed a dense hydrogen-bonded ANF matrix. Pure ANF-AE film achieved λ∥ of 7.7 W·m–1·K–1, as compared to conventional ANF-W. fGNP50/ANF-AE composite film achieved λ∥ of 81 W‧m⁻¹‧K⁻¹ and EMI SET of 57 dB at 60 μm. PDA-mediated fGNP/ANF coupling produced 368 MPa tensile strength and 20 MJ‧m-3 toughness. Hydrogen-bond reconstruction and fGNP interfacial coupling enabled multifunctional flexible films.