Interfacial flow and thermodynamics of imidazolium-based ionic liquids – oil lubricant

Ionic liquids (ILs) have enhanced tribological properties of lubricants when used as additives to conventional oils. In this work, we will use molecular dynamics simulations to study the dynamics and tribological properties of imidazolium-based ILs in hexadecane (model oil) lubricant confined between two iron slabs. Our preliminary study shows that ions create layered structures near the metal surface. These layers show strong adhesion to the surface since the free energy of adsorption greatly exceeds kT. To efficiently design ILs with target interfacial properties, we will characterize the dynamics of ions and oil molecules by calculating the non-affine mean-squared displacement at different shear rates. The stress response and flow behavior of the liquid will be tracked to understand the slip mechanism at the metal-IL and IL-oil interfaces.  Given that the stability of adsorbed layers depends on the orientation of molecules, we will quantify the local orientation along with the structure of ILs at these interfaces. This work will propose a model of IL-based additive to oils with controlled tribology as a more environmentally friendly solution for future lubricants.