Molecular Dynamics Simulation of Nanoconfined Ethanol–Water Mixtures

Molecular dynamics simulation was applied to study ethanol–water mixtures with different component contents that were confined between graphene surfaces. The effect of mixture component content and pore width on structural and dynamic properties and percolation of confined fluids were investigated and compared with the corresponding properties in bulk. All dynamic properties of water molecules significantly reduced because their movement is limited to a space in the middle of the box. Water molecules percolated in all mixtures and formed larger clusters compared to ethanol molecules. Also, percolation in confined systems happened with more probability compared to bulk systems. The segregation was found in a way that a layered structure with adsorbed ethanol molecules, with hydrophobe alkyl group, on graphene surface was formed specially in smaller pore width and dilute ethanol content mixtures. Diffusion coefficients of water and ethanol molecules in mixture are approximately comparable, so their different movement capability was balanced with interaction between water and ethanol. The ethanol–water hydrogen bond strength is more than the ethanol–ethanol hydrogen bond strength in bulk mixtures while it is less than its counterpart in the confined system, which is in agreement with segregation tendency in confined systems.