Thermal resistance of nanoscopic liquid-liquid interfaces: dependence on chemistry and molecular architecture

Systems with nanoscopic features contain a high density of interfaces. Thermal transport in such systems can be governed by the resistance to heat transfer, the Kapitza resistance (RK), at the interface. Although soft interfaces, such as those between immiscible liquids or between a biomolecule and solvent, are ubiquitous, few studies of thermal transport at such interfaces have been reported. Here we characterize the interfacial conductance, 1/RK, of soft interfaces as a function of molecular architecture, chemistry, and the strength of cross-interfacial intermolecular interactions through detailed molecular dynamics simulations. The conductance of various interfaces studied here, for example, water-organic liquid, water-surfactant, surfactant-organic liquid, is relatively high (in the range of 65-370 MW/m2 K) compared to that for solid-liquid interfaces ( approximately 10 MW/m2 K). Interestingly, the dependence of interfacial conductance on the chemistry and molecular architecture cannot be explained solely in terms of either bulk property mismatch or the strength of intermolecular attraction between the two phases. The observed trends can be attributed to a combination of strong cross-interface intermolecular interactions and good thermal coupling via soft vibration modes present at liquid-liquid interfaces.