Multiscale Modeling of Heat Conduction in a Hydroxyethyl Cellulose/Boron Nitride Composite Realizing Ultrahigh Thermal Conductivity via a “Moisture-Activated” Strategy

Polymer-based thermally conductive composites are widely used in microelectronics for heat dissipation and packaging, for which the filler arrangement and the filler/matrix interfacial thermal resistance (ITR) are key factors limiting superior thermal conduction realization. This work reveals the effects of filler modification and orientation on thermal duction in the boron nitride (BN)/hydroxyethyl cellulose (HEC) through multiscale simulation approaches. Nonequilibrium molecular dynamics (NEMD) identifies that the thermal conductivity of the BN molecule is not size-dependent and proves that thermal resistance is dramatically reduced after hydroxylation modification (BN_OH). Finite element simulation (FEM) reveals that maintaining a proper tilt of BN may improve both the cross-plane and in-plane thermal conductivity of the composite. Experimentally, BN_OH/HEC composites with high self-viscosity are prepared via a “moisture-activated” strategy, for which the introduction of BN_OH and wet hot pressing contribute to the thermal resistance reduction and filler orientation, respectively. The in-plane thermal conductivity reaches 30.64 W/mK with a cross-plane thermal conductivity of 5.06 W/mK. The films show good adaptability to surface morphology with the thermal resistance decreasing to 1.42 K·cm²/W. Practical thermal management demonstrates that the incorporation of BN_OH/HEC facilitates a 15.05 °C reduction of the LED Al substrate compared to the common composite film.