To investigate the effects of anion size, solvent content, and temperature on their physical properties, in this work, densities and viscosities of three binary mixtures, including ionic liquids (ILs) composed of the cation 1-hexyl-3-methylimidazolium (i.e., [C₆mim]⁺) and the halide anions (i.e., Cl^–, Br^–, and I^–), along with methanol (MeOH), were measured across the entire concentration range at temperatures from 288.15 to 323.15 K, and enthalpies of mixing were determined at temperatures of 298.15 and 308.15 K. Excess volumes and viscosity deviations were calculated to study the nonideal behavior of the mixtures. The results of excess volumes suggest that a combination of intermolecular interactions and packing effects contributes to their nonideal behaviors, with packing effects likely dominating the negative excess volume. Viscosity deviations and enthalpies of mixing indicate that MeOH molecules intend to coordinate with IL ions (IL cations and IL anions) in the IL-rich region, with stronger interactions observed between [C₆mim]Cl and MeOH compared to ([C₆mim]Br + MeOH) and ([C₆mim]I + MeOH) mixtures. Additionally, the nonrandom two-liquid model and the Gibbs–Helmholtz equation were combined to describe the enthalpies of mixing for the studied mixtures reliably.

中文翻译：

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离子液体 1-己基-3-甲基咪唑鎓卤化物与甲醇混合物的热力学研究

为了研究阴离子大小、溶剂含量和温度对其物理性质的影响，在这项工作中，研究了三种二元混合物的密度和粘度，包括由阳离子 1-己基-3-甲基咪唑鎓（即， [C ₆ mim] ⁺ ) 和卤化物阴离子（即 Cl ^-、Br ^-和 I ^-）以及甲醇 (MeOH) 在 288.15 至 323.15 K 的温度下在整个浓度范围内进行测量，热函为在 298.15 和 308.15 K 的温度下确定混合。计算过量体积和粘度偏差以研究混合物的非理想行为。过量体积的结果表明，分子间相互作用和堆积效应的结合导致了它们的非理想行为，其中堆积效应可能主导了负过量体积。粘度偏差和混合焓表明 MeOH 分子打算与富含 IL 的区域中的 IL 离子（IL 阳离子和 IL 阴离子）配位，与 ([C 6 mim]Cl 和 MeOH 之间观察_到更强的相互作用]Br + MeOH) 和 ([C ₆ mim]I + MeOH) 混合物。此外，将非随机双液模型和吉布斯-亥姆霍兹方程相结合，可靠地描述了所研究混合物的混合焓。