Quantification of the impact of water on the wetting behavior of hydrophilic ionic liquid: a molecular dynamics study

Abstract

ABSTRACT We have used molecular dynamics (MD) simulations to investigate the effect of water on the wetting behaviour and the interfacial structure of ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4] droplets on graphite surfaces which, is a prerequisite for the IL-based applications where the solid-fluid interface is involved. A slight decrement in the value of the contact angle has been found while adding water up to 17 wt% (∼0.68) afterward, the contact angle increases. The non-monotonic behaviour in the contact angle of IL-water droplet with the addition of water molecules was examined through several key parameters, such as solid-fluid interaction energy, the density profile of each species, 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.