Co-continuous Cu2P2O7/epoxy interpenetrating composites with near-zero thermal expansion and high thermal conductivity through tunable porous skeletons

Polymer-based composites typically suffer from a trade-off between thermal expansion and thermal conductivity due to the lack of continuous functional pathways. Herein, we propose a topological design strategy where Cu₂P₂O₇ is transformed from a passive filler into an active, tunable negative thermal expansion (NTE) skeleton to resolve this conflict. The scientific core of this work lies in regulating the sintering-mediated evolution of the porous skeleton to tailor the structure-property relationships. By precisely controlling sintering temperatures (1073 K–1373 K), we modulated the skeletal pore topology from a "particle-edge fusion" state to a highly densified network. This continuous NTE framework exerts a strong elastic constraint on the epoxy matrix, effectively suppressing its anharmonic vibration-induced expansion, while simultaneously eliminating phonon scattering at resin-particle interfaces to minimize interfacial thermal resistance. Consequently, the optimized CPO-1073/epoxy composite achieves a rare combination of near-zero thermal expansion (0.85 ppm K⁻¹) over a wide window (240–340 K) and high thermal conductivity (2.3 W m⁻¹ K⁻¹, seven times that of pure epoxy). Ideally, the low-temperature sintered skeleton preserves a high specific surface area for mechanical interlocking, ensuring robust structural integrity (∼80 MPa) unlike the brittle failure seen in dense ceramic networks. This work elucidates how preform-based microstructure engineering can independently tune thermal and mechanical functionalities, offering a generalizable principle for advanced composite design.