Modulating the thermal conductivity of crystalline nylon by tuning hydrogen bonds through structure poling

Abstract

The low thermal conductivity of polymers affects the reliability and functionality of devices. Tuning the hydrogen bonds inside them is one strategy to modulate their thermal conductivity. Here, using molecular dynamics simulation, we show that the thermal conductivity of crystalline odd-numbered nylons can be modulated by tuning the hydrogen bonds inside them through structure poling. Thermal conductivities along all directions can be increased after poling, and the thermal conductivity along the polarization direction in nylon 5 increases by a factor of three. Further analysis of morphology, H-bonds and vDOS shows that the increased density of inter-chain hydrogen bonds provides more effective heat conduction paths, and enhances structural order to facilitate phonon transport. And the change ratio of thermal conductivity after poling decreases as the nylon number increases. Investigation of thermal conductivity versus the electric field shows that the enhancement is transient after the field exceeds the threshold. Our study provides useful insight into the regulation of thermal transport in polymers.