Protic ionic Liquids-Water Interactions: A study on 2-Hydroxypropylammonium formate through experimental analysis and computer simulations

•IL 2-hydroxypropylammonium formate and water mixtures form highly organized structural systems.•High value of Angell’s D parameter indicates highly organized structural systems.•Formate anion establishes stronger interactions with water compared to 2-hydroxypropylammonium.•Thermal instability of the formed H-bond network proved by excess molar quantities.•Molar conductivity at high IL content in the mixture is affected by viscosity change with temperature. In this study, interactions within a mixture of the protic ionic liquid 2-hydroxypropylammonium formate and water were investigated across the entire range of ionic liquid compositions and a wide temperature range from 283.15 K to 333.15 K. This investigation was based on the measurement results of density, viscosity, and electrical conductivity, and was supported by computational simulations. The synthesized ionic liquid was further characterized thermally using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) techniques. The study focuses on the analysis of excess molar quantities of volume, thermal expansion coefficients, viscosity, and Gibbs energy of viscous flow, aiming to examine the influence of temperature and mixture composition on thermophysical properties. The impact of temperature on the system’s viscosity and Angell’s strength parameter was investigated to assess the influence of the ionic liquid’s content on the system’s structural organization. The dependency of molar conductivity on viscosity was analyzed through the Walden rule. Based on this analysis, the effect of temperature and mixture composition on deviations from the ideal behavior in diluted solutions of strong electrolytes was estimated. Computational molecular dynamics simulations were employed for a more detailed study of the structural organization of the system’s components.