Effect of interfacial energy transport of grafted polymers on the thermal conductivity of nanofluids

Abstract

Nanofluids exhibit enhanced thermal conductivity, yet their long-term dispersion stability remains a critical challenge. Polymer-grafted nanoparticles (PGNPs) improve stability and modify interfacial heat transport; however, how the polymer shell structure and its interplay with the nanolayer govern thermal conductivity is not fully understood. Here, equilibrium molecular dynamics simulations were performed to elucidate the interfacial mechanisms of heat transport in PGNP-based nanofluids. We systematically examined the effects of graft density and polymer--polymer binding energy on interfacial structures and thermal conductivity. At the highest graft density, thermal conductivity showed the strongest dependence on binding energy, reaching maximum enhancement at the highest binding energy and significant deterioration at the lowest binding energy. Structural analysis and decomposition of thermal conductivity revealed a transition from solvent--solvent dominated transport at low graft density to polymer-mediated (polymer--polymer and polymer--solvent) transport at high graft density. For weak polymer--polymer binding energy, enhanced polymer--solvent density overlap promotes interfacial energy transfer. These findings demonstrate that the organization of grafted polymers and their coupling with the nanolayer critically govern heat transport in PGNP-based nanofluids, providing design guidelines for high-performance nanofluids.