Tailoring Heat Transfer at Silica–Water Interfaces via Hydroxyl and Methyl Surface Groups

Efficient thermal transport across solid-liquid interfaces is critical for optimizing heat dissipation in modern technological applications. This study aims to investigate how surface functionalization affects heat transfer at the silica/water interface, with specific objectives: (i) to assess the impact of surface modification on interfacial thermal resistance (ITR) and (ii) to elucidate the physical mechanisms governing heat transfer on functionalized surfaces. We employ nonequilibrium molecular dynamics (NEMD) simulations of silica surfaces with varying concentrations of methyl and hydroxyl groups to quantify ITR and analyze the contribution of each functional group to the total heat flux. Results demonstrate that transitioning from methylated to hydroxylated groups leads to (i) an approximately 6-fold increase in adhesion energy, (ii) a reorientation of interfacial water molecules perpendicular to the surface normal, (iii) a reduction in liquid depletion length near the interface, (iv) a nonlinear decrease of ITR correlated with an increase in the number and strength of interfacial hydrogen bonds, and (v) enhanced dynamic stability of OH-mediated bonds, with OH-donor lifetimes exceeding those of CH₃-donor bonds by a factor of 5-6 and showing peak persistence at intermediate hydroxylation levels (∼50%). These findings highlight that manipulating the concentrations of functional groups enables precise tailoring of interfacial thermal transport, offering new opportunities for optimizing heat transfer in silica-based systems.