Synthesis And Evaluation Of Physicochemical Properties Of Two Kinds Of Choline Amino Acid Ionic Liquids And Their Aqueous Solutions

Due to their excellent physical and chemical properties,ionic liquids have been greatly developed in recent years and have been used in many applications in our life.Among them,choline amino acid ionic liquid,due to both of its cations and anions are natural products,rich in resources and cheap,has been widely concerned by researchers.There have been a lot of studies on choline amino acid ionic liquids in the past reports,but researches on the thermodynamic properties of their aqueous solutions are very few.In this paper,the development and classification of ionic liquids and the application of choline and amino acid ionic liquids are discussed,and then the synthesis of choline glycine[Ch][Gly]and choline alanine[Ch][Ala]ionic liquids,the main research content is as follows:The products were analyzed by ~1H NMR and ¹³C NMR,and obtained as the target ionic liquids.The ionic liquids+H₂O binary systems with molar fraction of0～1.0000 were prepared by mixing the ionic liquids with water.In the temperature range of 288.15-333.15 K,with intervals of 5 K:（1）The densities,viscosities,surface tensions and refractive indexes of pure ionic liquids were measured by standard addition method;（2）Densities,viscosities,surface tensions and refractive indexes of ionic liquids+H₂O binary systems were measured.Firstly,the excess molar volume（V^E）and the mean molar volume（V_m）were calculated from the density values of the binary systems,and V^E was fitted by Redlick-Kister equation.The fitting results show that the relation between V^E and the molar fraction of ionic liquids is an asymmetric parabola,and the absolute value of V^Edecreases with the increase of temperature.Secondly,viscosity deviation（Δη）,excess Gibbs free energy of viscous flow activation(ΔG^≠E)and excess entropy of viscous flow activation(ΔS^≠E)were calculated by viscosity values of binary systems.The values ofΔηandΔG^≠E are all negative values.The positive viscosity deviation indicates that the intermolecular interaction is dominant in the mixture,while the negative viscosity deviation indicates that the intermolecular interaction is weak.Therefore,the intermolecular interaction of[Ch][Gly]+H₂O and[Ch][Ala]+H₂O binary systems is weak.ΔηandΔG^≠E are fitted by Redlick-Kister equation.The results show that the absolute values ofΔηandΔG^≠E decrease gradually with the increase of temperature.With the increase of the molar fraction of ionic liquid,the absolute value ofΔηandΔG^≠E increases first and then decreases.The refractive index deviation（Δn_D）was calculated by the refractive index values of binary systems.Δn_D is positive.Δn_D was fitted by Redlick-Kister equation.It is found thatΔn_D is more affected by ionic liquid mole fraction than by temperature.Finally,the molar surface Gibbs energy（g_s）,molar surface entropy（s）and molar surface enthalpy（h）of the binary mixtures were calculated by the surface tension and density of the binary systems.The effects of temperature and mole fraction on g_s and h were studied.With the increase of temperature,g_s decreases,but not significantly.With the increase of ionic liquid mole fraction;g_s increases.h increases with the increase of the molar fraction of ionic liquid,but is almost constant with the increase of temperature.