离子液体1-甲基-3-乙基咪唑四氟硼酸盐和1,2-二甲基-3-乙基咪唑四氟硼酸盐的热力学和电导性质研究

Thermodynamic and electrical conductivity properties of ionic liquids 1-ethyl-3-methyllimidazolium tetrafluoroborate and 1,2-dimethyl-3-ethyllimidazolium tetrafluoroborate

在室温下合成了离子液体1-甲基-3-乙基咪唑四氟硼酸盐([Emim]BF4)和1,2-二甲基-3-乙基咪唑四氟硼酸盐([Dmeim]BF4),通过红外光谱对其进行了结构表征。分别测定了两种离子液体在不同温度下的密度、表面张力、粘度和电导率,发现当咪唑环2位碳上增加甲基取代基后其密度、表面张力和电导率均呈下降趋势,而粘度呈上升趋势且变化较大,如在298.15 K时[Emim]BF4的粘度为842 mPa.s,[Dmeim]BF4的粘度为8 293 mPa.s。并根据特定的经验方程估算了两种离子液体的热膨胀系数、摩尔体积、标准熵和晶格能等重要的性质参数。

Two types of ionic liquids l-ethyl-3-methyllimld- azolium tetrafluoroborate [ Emim ] BF4 and 1,2-dimethyl-3-ethyllimidazolium tetrafluoroborate [ Dmeim ] BF4 were synthe-sized at room temperature, and the structures were confirmed by FT-IR. The properties of two ionic liquids such as surface tension, density, viscosity and electrical conductivity were measured at different temperatures. The results showed that there were decreases in surface tension ,density and electrical conductivity and the viscosity was substantial increased, which was resulted from the substituted 2-position C of the cation by methyl. For example, at 298.15 K the viscosity of [ Emim] BF4 was 842 mPa. s, [ Dmeim] BF4 was 8 293 mPa· s. The thermal expansion coefficient, molar volume, standard entropy and crystal energy were also estimated by the empirical equa-tions.