Pressure-induced thermal conductivity optimization in polyimide materials for gravitational wave detection systems

Gravitational wave detection systems require high-stability precision equipment, making the control of thermal conductivity in applied materials essential for stable operation. Grounded in molecular dynamics theory, this study aims to enhance the thermal conductivity of polyimide (PI) materials through the application of external pressure. The Reverse Non-Equilibrium Molecular Dynamics (RNEMD) method was used to investigate the heat transfer mechanisms in PI structures under different compression pressures. The results show significant thermal conduction along polymer chains when the chain length exceeds 15 monomers. This observation aligns with the thermal conductivity mechanisms of actual molecular chain polymers, accurately reflecting the structural behavior of PI. Furthermore, when continuous pressure was applied between 0 and 12 GPa, complex patterns of thermal conductivity emerged. Initially, thermal conductivity exhibited an upward trend, followed by a decrease, and finally a rise with increasing pressure, resulting in at least a 40 % increase in thermal conductivity. The dynamic changes in thermal conductivity are attributed to complex variations in molecular interactions and heat conduction pathways. Moderate compression enhances effective phonon transport between molecules, whereas excessive compression induces structural disorder, thereby reducing thermal conductivity. The study also examined the impact of model density and structural changes on thermal conductivity during compression. With the same structure, thermal conductivity exhibited a gradual increase with rising density. However, within the density range of 1.6 to 1.9 g/cm³, thermal conductivity showed a significant increase. At consistent density, thermal conductivity abruptly decreased at lower compression levels. With increased compression, thermal conductivity changes gradually leveled off. This comprehensive study delved into the interactions between chain length, pressure, and structural factors affecting the thermal conductivity of PI materials. These findings provide an important theoretical foundation for the development and design of new materials, potentially optimizing the thermal management performance of gravitational wave detection systems.