An experimental and computational study on the excess properties and molecular interactions of binary mixture of (1-ethyl-3-methylimidazolium ethylsulfate +2-methyl-1-propanol) at temperatures of (298.15 to 323.15) K

In this paper, thermophysical properties, densities (ρ), sound velocities (u), and dynamic viscosities (η) of pure ionic liquid(IL), 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) and molecular solvent, 2-methyl-1-propanol (2M1P), and their binary mixture (EMIM[EtSO4] + 2M1P) have been measured over the temperature range of 298.15 K to 323.15 K with an interval of 5 K at constant pressure, 1 atm. We further studied the effect of IL concentration influencing the thermophysical properties of the binary mixture (EMIMEtSO4 + 2M1P). To understand the possible mechanism of interaction and deviation from ideal mixing behaviour, excess molar volumes VE, excess isentropic compressibility κsE, and dynamic viscosity deviations (Δη) have been calculated. The Redlich-Kister equation has been employed to determine the fitting parameters (Ai), correlation coefficients (R2), and the standard deviations (σ), which collectively reflect the fitting of the experimental data. The Prigogine-Flory-Patterson (PFP) theory has been used to assess interactions by quantifying their contribution to interactions in a binary mixture. In addition, density functional theory (DFT) calculations have been performed for pure IL and their binary mixture. The extracted key parameters, including the HOMO-LUMO gap, reduced density gradient (RDG), non-covalent interaction (NCI), molecular electrostatic potential (ESP) diagram, and reactivity descriptors, help elucidate the nature of interaction in the system. Furthermore, molecular dynamics (MD) simulations have been conducted for both pure and their binary mixture at 298 K to gain atomic and molecular-level insights. This study provides data on density, radial distribution function (RDF), coordination number, and other dynamical properties, including mean square displacement (MSD) and self-diffusion coefficient (D). © 2026 Elsevier B.V.