Quantification of the Impact of Water on the Wetting Behavior of Hydrophilic Ionic liquid: A Molecular Dynamics Study

We have used molecular dynamics simulations to study the effect of water on the wetting behavior and the interfacial structure of ionic liquid (IL) 1-ethyl-3-methylimidazolium boron tetrafluoride[EMIM][BF4] droplets on graphite surfaces which, is a prerequisite for the new IL-based applications in the field of chemical engineering. A slight decrement in the value of the contact angle has been found while adding water up to 20wt%; afterward, the contact angle starts to increase. The non-monotonic behavior of contact angle of IL droplet with the addition of water molecules was examined through several key parameters, such as the interaction energies between the graphite and IL molecules, density distributions, cluster formation, and the number of formed hydrogen bonds (HBs) for the different weight percentages of water molecules. The results indicate that the hydrogen bond network and the cluster formation among the water molecules play a vital role during the transition from IL rich medium to water-rich medium of the droplet.