Interfacial thermal conductance between a polyethylene glycol polymer chain and water: A molecular dynamics study

Understanding interfacial heat transfer between polymers and water is crucial for the design of biomaterials, drug delivery platforms, and nano-fluidic systems. In this study, we employed all-atom molecular dynamics (MD) simulations to quantify the interfacial thermal conductance between an infinitely diluted polyethylene glycol (PEG) 36-mer chain and explicit water over the temperature range of 280-350 K. To compare the conformational behavior of the PEG chain, we examined its radius of gyration and observed a temperature-dependent chain collapse consistent with previous coarse-grained models. By employing a transient non-equilibrium MD approach, we imposed temperature difference across the interface and analyzed the energy relaxation behavior to compute heat transfer across the polymer-water interfaces. Moreover, we investigate the impact of polymer conformation on heat transfer by considering modulations of the Lennard-Jones polymer/solvent interactions, different from the original PEG-water interactions. Our results demonstrate that both temperature and Lennard-Jones interfacial interaction strength influence interfacial thermal conductance, with temperature playing the dominant role. Structural factors such as chain conformation and interfacial area were found to mediate the effect of interfacial interaction. Additional analysis of the vibrational density of states and the mean square displacement reveal that vibrational coupling has minimal impact on thermal conductance across interfaces, whereas increased water thermal motion enhances energy transfer. These findings highlight the structural and dynamical origins of interfacial thermal conductance and provide atomistic insights into the tuning of interfacial heat transport in molecular systems through temperature and solvent interactions.