吡啶基离子液体[C_6py][DCA]热力学性质及利用新E?tv?s方程预测其表面张力

制备了吡啶类离子液体N-己基吡啶二氰胺盐C_6py]DCA],并用核磁共振氢谱(~1H NMR)、核磁共振碳谱(~(13)C NMR)、差热扫描量热(DSC)、傅里叶变换红外(FT-IR)光谱对其进行表征。在288.15–338.15 K温度范围内,采用标准加入法,测定其密度(ρ)、表面张力(γ)和折光率(n_D)。在测得的实验数据的基础上,得到了离子液体C_6py]DCA]的分子体积(V_m)、表面能(E_a)、摩尔极化度(R_m)和极化率(α_p)。结果显示E_a、R_m和α_p几乎不随温度的变化而发生改变。本文还提出了摩尔表面Gibbs自由能(g_s)的概念,并改进了E?tv?s方程。同时还计算了gs、临界温度(T_c)和E?tv?s方程经验参数(kE),并预测了离子液体C_6py]DCA]的表面张力,预测值与实验值具有较好的一致性。

Thermodynamic Properties and Predicting the Surface Tension of Pyridinium-Based Ionic Liquids of [C6py][DCA] Using a New Eötvös Equation

The pyridinium-based ionic liquids C₆py]DCA] (N-hexyl-pyridinium dicyanamide) was prepared and characterized using 1]H and 13]C nuclear magnetic responancec (NMR) spectroscopies, Fourier transform infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). The density (ρ), surface tension (γ), and refractive indices (n_D) were measured at the temperature range from 288.15 to 338.15 K. Molecular volume (V_m), energy of surface (E_a), molar polarization (R_m), and polarization coefficient of C₆py]DCA] (α_p) were calculated from the experimental data. E_a, R_m, and α_p were approximately temperature-independent. The concept of molar surface Gibbs free energy (g_s) was conceived, for which a new Eötvös equation was derived. The g_s, critical temperature (T_c), and Eötvös empirical parameter related to polarity (k_E) were also obtained. The new Eötvös equation was used to predict the surface tension and the predicted values of C₆py]DCA] are in close agreement with the corresponding experimental ones.