Enhanced interfacial thermal transport in diamond nanothread reinforced polymer nanocomposites: insights from atomistic simulations and density functional theory

Diamond nanothreads (DNTs), a novel class of nanomaterials that outperform traditional carbon-based nanomaterials, are exceptional reinforcers for advanced polymer composites and hold great promise in various applications of composites. In this atomistic simulation study, the novelty lies in the comprehensive exploration of DNT-polymer interfacial thermal conductance and the identification of methyl functionalization as a superior strategy, with clear implications for designing advanced thermal management composites. It is found that DNTs, derived from surface modifications (i.e. hydrogenation and functionalization) of carbon nanotubes (CNTs) with a chirality of (3, 0), demonstrate significantly enhanced interfacial thermal conductance in nanocomposite systems compared to unmodified CNTs. In particular, the incorporation of DNT_C-CH₃ achieves the highest interfacial thermal conductance of 0.115 GW m⁻² K⁻¹, signifying a 140% improvement over CNTs. Through analyzing the phonon density of states (PDOS) of different reinforcements and a paraffin wax matrix, it is revealed that the low-frequency (0-70 THz) phonons dominate the interfacial thermal conductance due to their more significant contribution compared to the high-frequency (70-120 THz) phonons. Among all interfacial material combinations, DNT_C-CH₃/paraffin wax exhibits the best matching in terms of the PDOS overlap, the PDOS peak intensity and the PDOS peak position in the low-frequency regime, which facilitates the most effective phonon transport across the interface and thereby leads to significant enhancement in interfacial thermal conductance. Furthermore, density functional theory (DFT) calculations uncover the optimal molecular electrostatic potential distribution and the highest binding energy of DNT_C-CH₃/paraffin wax molecular structures, indicating excellent interfacial compatibility and strong adhesion between the reinforcement and the matrix material, which plays an important role in enhancing the interfacial thermal conductance. The findings of this study not only deepen the understanding of the physical mechanisms governing interfacial thermal conductance but also highlight the great potential of DNT reinforced composites in advanced thermal management applications.