离子液体[Pmmim][SCN]+乙腈二元混合体系的热力学性质及超额性质研究

The thermodynamic and excess properties of [Pmmim] [SCN] ionic liquids with thiocyanate and its binary systems with acetonitrile

文中合成并表征了一种新型离子液体1-丙基-2,3-二甲基咪唑硫氰酸盐([Pmmim][SCN]).并将该离子液体与有机溶剂乙腈(ACN)混合,制备成全浓度二元混合体系.对288.15 K,298.15 K,308.15 K,318.15 K温度下这种新型离子液体及其混合体系的密度、电导率和粘度进行了测定.根据Vogel-Fulcher-Tamman(VFT)方程和Arrhenius方程对二元混合体系的粘度、电导率进行拟合,并对体系粘度、电导率随温度的变化情况进行了描述.此外还根据经验和半经验公式估算了离子液体的热膨胀系数、分子体积、标准熵和晶格能.最后计算了该混合体系的超额摩尔体积和粘度偏差,结果表明全浓度体系范围内的超额摩尔体积和粘度偏差均呈现负值,说明了离子液体与溶剂分子之间存在氢键作用.

1-propyl-2,3-dimethylimidazolium thiocyanate（ [Pmmim][SCN ]） was synthesized and characterized by various methods. Then the [Pmmim][SCN] was blended with acetonitrile（ ACN） to prepare binary IL-based mixture system over the whole concentration range（ molar ratio of IL from 1 to 0）. The densities,electrical conductivities,and dynamic viscosities of the IL and the binary system were determined at 288. 15 K,298. 15 K,308. 15 K,318. 15 K. The temperature dependence of the transport properties（ dynamic viscosity and electrical conductivity） are described by the Vogel-Fulcher-Tamman（ VFT） equation and Arrhenius equation,respectively. The volumetric properties like thermal expansion,coefficient,molecular volume,standard molar entropy,and lattice energy of the IL are estimated through the empiric/semiempirical methods. The excess molar volumes（ V^E） and dynamic viscosity deviations（ Δ_η） of the mixtures are calculated. The negative values of the entire composition range of excess properties clearly indicate the existence of hydrogen-bond interaction between the studied components.