Dual‐Ordering Strategy for Simultaneous High‐Strength and High‐Thermal‐Conductivity Phthalonitrile Composites via Liquid Crystal Engineering

ABSTRACT Developing polymer composites with simultaneous high thermal conductivity and mechanical integrity remains challenging due to interfacial phonon scattering and the filler‐loading trade‐off. Herein, a hierarchical “dual‐ordering” strategy is proposed to construct high‐performance structural‐functional integrated materials by synergizing a thermotropic liquid crystalline phthalonitrile (LCPN) matrix with cyanobiphenyl‐based mesogen‐functionalized graphene (CBN‐G). This strategy operates on two synergistic levels: the in situ locking of nematic liquid crystalline domains within the matrix and the construction of a covalent “phonon‐matching” gradient interface. The pristine resin matrix thereby achieves a high intrinsic in‐plane thermal conductivity of 0.71 W m − 1 K − 1 . Crucially, the interfacial ordering is theoretically validated by non‐equilibrium molecular dynamics (NEMD) simulations to reduce interfacial thermal resistance by ∼79% via enhanced vibrational resonance. Consequently, the resulting composite delivers an exceptional in‐plane thermal conductivity of 6.55 W m − 1 K − 1 at a low loading of 10 wt.%. Furthermore, the robust covalent bridging transforms the failure mechanism from adhesive to cohesive, boosting the flexural strength to 123 MPa—an improvement of 89% over physically blended counterparts. This work not only elucidates the atomic‐scale mechanism of interfacial phonon transport but also establishes a versatile engineering paradigm for next‐generation thermal management systems in extreme environments.