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

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.