Lower Limit of Interfacial Thermal Resistance across the Interface between an Imidazolium Ionic Liquid and Solid Surface

Understanding of energy transport across the solid–liquid interface is essential for the rational design of efficient heat dissipation capabilities. In this work, we show that the molecular orientation of liquid near the solid surface dominates the thermal transport across the imidazolium ionic liquids (IL)/graphene interface via molecular dynamics simulations. The molecular orientation is defined as the parallelism between the imidazole ring in IL and graphene and is controlled by wettability of graphene. Interfacial thermal resistance (ITR) will decrease linearly with the parallelism, which is suitable for IL with different tail chain length (2, 4, 6, and 8). From the linear relationship, a lower limit of ITR for the IL–graphene interface can be predicted, which is on the order of ∼6 m2K/GW and stands for the lower bound of ITR across the solid–liquid interface. Furthermore, it is indicated that the parallel imidazole ring in IL facilitates the thermal transport via shifting the dominating vibrational modes to a higher frequency (∼15 THz). These findings show that the molecular orientation can be an effective factor to control the interfacial thermal transport, which can shed light on the future rational designs of some key chemical engineering processes, such as IL-based coolants, batteries, nanoelectrical devices, and so on.