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• The V E and Δ η values of all mixtures exhibit negative deviation over the mole fraction range. • Based on VFT equation and Arrhenius empirical equation, there is a high correlation σ and T. • [MOEMPYrr]+ acts as HBD and [TFSI]- (or solvent) acts as HBA using the COSMO-RS model. • The interaction between anions and cations in the ILs + PC is stronger than in the ILs + GBL. • In terms of Einstein's equation, D GBL or D PC > D + [MOEMPYrr] > D - [TFSI]. A deeper comprehension of the mechanism behind various internal interactions and their influence on system properties encourages the utilization of ionic liquid mixture systems. In this work, the excess molar volume, viscosity deviation, change of electrical conductivity, and ionicity of both binary mixtures for N-methyl-N-methoxyethylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([MOEMPYrr][TFSI]) ether-functionalized ionic liquids (ILs) with 1,4-butyrolactone (GBL) or propylene carbonate (PC) were systematically studied. The specific interactions between ILs and solvent molecules were investigated by using the COSMO-RS model in terms of DFT calculation. The results indicate that [MOEMPYrr]+ tends to act as a hydrogen bond donor and [TFSI]- tends to act as a hydrogen bond acceptor, and GBL (or PC) has a strong hydrogen bond acceptance ability. Furthermore, based on the radial distribution functions (RDFs) from molecular dynamics (MD) simulations, the H 1 atom in [MOEMPYrr]+, the O 2 atom in [TFSI]-, the O 3 atom in GBL, and the O 4 atom in PC are selected as reference sites to study the interaction between cations and anions (or solvent molecules). It is found that the interaction between anions and cations in the [MOEMPYrr][TFSI] + PC system is stronger than that in the [MOEMPYrr][TFSI] + GBL system, and the interaction between cations and GBL is stronger than that between cations and PC. This result further explains why the excess molar volumes (V E) of [MOMPYrr][TFSI] + GBL binary mixtures are greater than that of [MOMPYrr][TFSI] + PC binary mixtures from a microscopic perspective. [ABSTRACT FROM AUTHOR]

• Three ether-functionalized ionic liquids were prepared and characterized. • The surface tension, density and refractive index of EFILs were measured. • The thermodynamic properties of EFIILs were studied. • A new method for estimating Δg l C p o m of ILs was put forward. • The concept of the polarity coefficient P for ILs was proposed. Ether groups are well-known for their unique contribution to low viscosity and high conductivity, hence ether-functionalized ionic liquids (EFILs) have been widely studied and successfully employed in various applications. Three EFILs 1-(2-methoxyethyl)-3-methylimidazolium chloride, 1-(2-ethoxyethyl)-3-methylimidazolium chloride and 1-(2-ethoxyethyl)-3-methylimidazolium bromide were prepared and characterized. Their surface tension, density and refractive index in the range of T = (288.15–328.15) K were measured and the molar surface Gibbs energy, g s , were calculated. Combined g s with Lorentz-Lorenz equation, an expression for predicting surface tensions of ionic liquids was obtained, and the predicted values were in good agreement with the experimental ones. According to the g s , the vaporisation enthalpies were predicted and the association enthalpies of ionic liquids were estimated. A new method for estimating the difference of heat capacities between the vapour phase and the liquid phase of ionic liquids was put forward, and the estimated values were in the same order of magnitude as the Verevkin method. Moreover, the concept of the polarity coefficient P for ionic liquids was proposed and the polarity of many ionic liquids was estimated. [ABSTRACT FROM AUTHOR]

The ether-functionalized imidazolium ionic liquids (IL) applied in the silica sol–gel process demonstrated a defined coordination potential. These IL display the capacity to control the system organization from the reactions’ first moments through a dynamic system-assembling ability, being the sum of ionic and physical interactions, i.e. Coulomb forces, H-bonding and London forces. The initial hydrolysis steps of tetraethyl orthosilicate (TEOS) in the presence of these IL were followed by Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS), both in time-resolved experiments, in an attempt to correlate the structuring and the bonding dynamics of these systems. [ABSTRACT FROM AUTHOR]

• [C 1 OC 2 mim][OAc], [C 1 OC 2 mim][Pro] and [C 2 OC 2 mim][Pro] were synthesized and characterized. • The volume, viscosity and electrical conductivity properties of samples were investigated. • The variation trend of η (or k) and T of samples was investigated by VFT equation. • The activation energies of samples were calculated by Arrhenius empirical equation. • The activation Gibbs energy values for viscous flow of samples were obtained by Eying viscosity equation. 1-(2-Methoxyethyl)-3-methylimidazolium acetic acid ([C 1 OC 2 mim][OAc]), 1-(2-methoxyethyl)-3-methylimidazolium propionic acid ([C 1 OC 2 mim][Pro]) and 1-(2-ethoxyethyl)-3-methylimidazolium propionic acid ([C 2 OC 2 mim][Pro]) were successfully prepared by two-step synthesis method. Based on the standard addition method, the physicochemical parameters of the density, viscosity and electrical conductivity for ether-functionalized ionic liquids (ILs) were measured. The volume properties of three ether-functionalized ILs and their homologues were estimated by semi-empirical methods. According to the Eying viscosity equation, the relationship between viscosity and activation Gibbs energy for viscous flow (Δ G ≠) was studied. The activation energy values for three ether-functionalized ILs were calculated by Arrhenius empirical equation. The activation energies of these ether-functionalized ILs are arranged in the following order: [C 1 OC 2 mim][Pro] (E η = 39.17 kJ·mol−1) > [C 2 OC 2 mim][Pro] (E η = 37.26 kJ·mol−1) > [C 1 OC 2 mim][OAc] (E η = 37.23 kJ·mol−1). Futhermore, the Vogel-Fulcher-Tamman (VFT) equation is used to describe the relationship between viscosity (or electrical conductivity or molar electrical conductivity) and temperature, and the experimental results show that VFT equation has good general applicability. [ABSTRACT FROM AUTHOR]

• △ V E/△ T is described the interaction between the solvent and solute quantificationally. • The g s increases with the increase of x 1 , while it is quite small changes with T. • Based on g s , surface tension γ is estimated and γ est is in good agreement with γ exp. The density and surface tension for the binary mixtures of ionic liquid (ILs) [C 2 2O1IM][TfO] with ethanol, 1-propanol and 2-propanol are measured across the entire range of mole fraction at T = (288.15–318.15) K. The excess molar volumes of the binary mixtures are calculated, the relationship between V E and the mole fraction and temperature are explored. Especially, the term, △ V E/△ T is proposed to describe the interaction between the solvent and solute quantificationally. The molar surface Gibbs energy of the binary mixtures are obtained based on the density and surface tension, and the interaction between the components in both liquid and surface phase of the binary mixture is discussed. And its applications are also explored, including the estimation of surface tension for the binary mixtures and the improvement of the traditional Eötvös equation. At the same time, the polarity of the binary mixtures of [C 2 2O1IM][TfO] with alcohols is obtained. [ABSTRACT FROM AUTHOR]