Highly Thermally Conductive and High Shear Strength Graphene Fiber Composites via Molecular Conjugation Interface Engineering for Extreme Thermal Management

ABSTRACT Highly thermally conductive graphene fibers (GFs) hold exceptional promise for next‐generation high‐flux thermal management systems, yet their integration into advanced composites remains fundamentally limited by insufficient interfacial compatibility with polymer resin. This limitation severely restricts both thermal and mechanical transfer efficiency and compromises stability under extreme thermal cycling. Herein, a molecularly tailored conjugation interfaces engineering through strategically selected silane‐based molecular tethers grafted onto the wrinkled GF surfaces to establish covalent bridges into the epoxy network, effectively addressing the interfacial bonding dilemma between GFs and polymer resin is introduced. The resultant GF composites achieve a synergistic enhancement in interfacial shear strength increased by 61.6% (from 55.2 to 89.2 MPa) and a record‐level in‐plane thermal conductivity of 571.1 W m −1 K −1 . Critically, the thermal conductivity retention consistently exceeds 98% throughout 100 thermal shock cycles (25 to 125°C), confirming exceptional interfacial stability and thermal fatigue resistance. Furthermore, molecular dynamics (MD) simulations reveal that rigid benzene ring of molecular tethers interphase enables exceptional interfacial thermal conductance of 373.56 MW m −2 K −1 between graphene and epoxy, while flexible or mismatched molecular tethers agents induce disorder and weaken spectral coupling. This molecular conjugation interface engineering unlocks the interfacial design and chemistry for improving thermomechanical performances of GF composites, paving the way for robust and high‐flux thermal management.