Molecular insights on the microstructures of nanoconfined glycerol and its aqueous solutions: The effects of interfacial properties, temperature, and glycerol concentration

In this work, we conducted molecular dynamics simulations to investigate the effects of rutile–liquid and graphene–liquid interfacial properties, glycerol concentrations (i.e., 10%, 40%, 70%, and 100% molar contents), and temperature (i.e., 180, 273, and 320 K) on the microstructures of nanoconfined glycerol and its aqueous solutions. Results indicated that the effect of interfacial properties on the spatial and orientation distributions of nanoconfined glycerol and water molecules was more prominent than that of temperature. In glycerol aqueous solutions, water and glycerol molecules localized into two distinct layers on the hydrophilic rutile surface but partially mixed with each other near the hydrophobic graphene surface, because water molecules near the hydrophobic surface exhibited more random orientations and formed more hydrogen bonds with glycerol molecules than those near the hydrophilic surface. Moreover, interface introduction and increased temperature drastically reduced the hydrogen bonding ability of water molecules in glycerol aqueous solutions. The addition of glycerol molecules can break hydrogen bonds between water molecules and inhibit water crystallization in glycerol aqueous solutions. Temperature and glycerol concentration exerted limited effects on the hydrogen bonding ability of water molecules on hydrophilic surfaces in glycerol aqueous solutions. Meanwhile, the presence of a hydrophilic surface can effectively decelerate hydrogen bond breakage induced by increasing temperature or by decreasing glycerol contents.