Shear Viscosity of Quasi-Two-Dimensional Ionic Liquids

The shear viscosity (η) and kinetic friction coefficient (μ) of highly confined, quasi-two-dimensional ionic liquids (2D ILs) subject to stationary linear flow at constant temperature are studied in this work through coarse-grained numerical simulations. Using stationary state linear flow under increasing shear rate (γ̇), η and μ are predicted as functions of γ̇ for growing coupling constant values (Γ*). The structural changes of the fluid due to the increasing coupling of the charged particles are found to yield increasing shear viscosity and friction coefficient. Shear-thinning is found in all systems, regardless of the value of Γ*. Additionally, it is shown that η and μ obey universal scaling laws, η ∼ γ̇^ζ and μ ∼ γ̇^κ, respectively, with the exponents fulfilling the relationship κ - ζ = 1, in agreement with previous reports by other groups. The implications of our predictions are discussed, in the context of current applications.