Study Of The Thermodynamic Properties Of Ether-functionalized Ionic Liquids [MOEMIm]Cl And [EOEMIm]Cl

Due to the unique nature of the ether group,two ether-functionalized ionic liquids[MOEMIm]Cl and[EOEMIm]Cl were synthesized by using ether-imidazole groups as cations and chloride ions as anions,and by nuclear magnetic resonance spectroscopy（¹H NMR）,NMR(¹³C NMR),thermogravimetric analysis.The nuclear magnetic resonance spectrum showed the target product no impurity peak.The whole thermogravimetric analysis showed that the initial decomposition temperatures of[MOEMIm]Cl and[EOEMIm]Cl were 568.15 K and 553.15 K,respectively,which confirmed the high temperature stability of the two ionic liquids.The density（?）,surface tension（?）and refractive index（n_D）of the ionic liquids[MOEMIm]Cl and[EOEMIm]Cl were measured at temperatures ranging from288.15 K to 328.15 K.Based on the measured density data,the volume properties of their were calculated and discussed using the definition of thermal expansion coefficient（?）.According to Glasser’s theory,298 K standard entropy（S₀）and lattice energy(U_POT)can be obtained,and the volume,standard entropy and lattice energy of five ether-functionalized ionic liquids similar to those of ionic liquids are discussed.Based on the thermodynamic relationship,the molar surface Gibbs free energy（g_s）,molar surface entropy（s）,molar surface enthalpy（h）,molar polarization（R_m）and molar polarizability（α_p）of they were calculated.From the calculation results,the molar surface enthalpy at different temperatures is approximately constant,which also indicates the process from the inside to the surface of the two ionic liquids.It is an equal coulomb process,and the molar and molar polarities of the two ionic liquids are independent of temperature.The Lorentz–Lorenz equation was also improved by the molar surface Gibbs free energy and used to predict the surface tension of ionic liquids[MOEMIm]Cl and[EOEMIm]Cl at different temperatures.The predicted values are highly correlated with the experimental values.