Thermophysical, acoustic and optical properties of binary mixtures of imidazolium based ionic liquids + polyethylene glycol

• Density, speeds of sound and refractive index was measured at T = (293.15–323.15) K at 5 K interval.
• Volumetric, acoustic and optical properties of binary mixtures involving ionic liquids and PEG 400.
• Excess molar volume estimated using the PFP theory and ERAS model.
• Deviation in refractive index was calculated.
• nD of binary mixtures were correlated by mixing rules.

In this manuscript, we have reported first time the densities, ρ, speeds of sound, u  , and refractive indices nDnD for pure 1-alkyl-3-methylimidazolium bromide [Cnmim][Br] (n = 4, 6 and 8), poly ethylene glycol 400 and their binary mixtures at 0.1 MPa, covering entire range of compositions and temperature ranges from 293.15 K to 323.15 K. The measured properties have been used to derive excess molar volumes, VmE, excess molar isentropic compressibilities, Ks,mE, and refractive indices deviation, Δ∅nDΔ∅nD. The values of VmE, Ks,mE and Δ∅nDΔ∅nD have been fitted to Redlich–Kister polynomial equation for evaluation of binary coefficients. The variation in excess properties have been discussed in terms of hydrogen bonding and ion-dipole interaction. The VmE and Ks,mE were largely negative and decrease with increasing temperature and size of alkyl chain of ionic liquid. The Δ∅nDΔ∅nD is small negative. The experimental nDnD of the binary mixtures were predicted by several mixing rules. The experimental VmE were reviewed by Prigogine–Flory–Patterson (PFP) theory and Extended real association model (ERAS).

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