The Thermodynamic Propertiesand Intermolecular Interactions Of Ether-Based Cationic Functionalized Ionic Liquids And Their Binary Mixture Systems

Ionic liquids?ILs?are salts that are liquid at room temperature and consist of cations composed of organic macromolecules and anions composed of inorganic acids.ILs have the advantages of low vapor pressure,stable chemical properties,strong solubility,non-volatile,stable electrochemical properties,,and recycling.However,generally the high viscosity of pure ionic liquid leads to its weak transport performance,which limits its application range to some extent.Through literature research and previous work,it is found that the mixing system of ionic liquid with specific organic solvents can effectively reduce the viscosity and improve the performance.In addition,according to the designable characteristics of ionic liquid,the physicochemical properties of the mixed system can be predicted at the beginning of the composition of the mixed system,which provides theoretical support and innovative ideas for obtaining better ionic liquid or mixed system.This paper synthesized two contain different cationic ether functionalized ionic liquids,1-ethyl methyl ether-3-methyl imidazole trifluoro methanesulfonyl imine?[MOEmim][NTf₂]?,ethyl methyl ether-3-N-methyl pyridine double sulfonyl fluoride imide salt?[MOEmpy][NTf₂]?,and two kinds of ionic liquids respectively mixed with acetonitrile?AN?and 4-hydroxy butyric acid lactone?GBL?to form 4binary mixture systems inwhole concentration range,and the thermodynamics properties of the four mixtures were measured under different temperatures,such as,density???,viscosity???,and electrical conductivity???.For the thermodynamic properties of pure ionic liquids,we estimate the thermodynamic parameters that cannot be directly measured based on empirical or semi-empirical equations,such as molecular volume V_m,thermal expansion coefficient?,porosity,and lattice energy U_POT.For the binary systems,the Vogel-Fulcher-Tamman?VFT?equation and Arrhenius equation were used to describe the relationship between viscosity/conductivity and temperature.Based on the measured density values,the excess molar volume?V^E?of the binary system is estimated,and the Redlich-Kister?R-K?polynomial equation is used to fit the V^E.The intermolecular intereactions are one of the root causes of the change in the thermodynamic properties of the binary mixture systems.In order to explore the micro-effects of the binary system,based on density functional theory?DFT?,the interaction energy of the ionic liquid anions,cations,acetonitrile?AN?and 4-hydroxybutyrolactone?GBL?molecules,structure and hydrogen bonding between molecules were calculated by DFT method.The internal microscopic effect of the ionic liquid binary system and its influence on the thermodynamic properties are discussed.