Department of Chemistry, School of Sciences, Harbin Institute of Technology, Harbin 150001, Heilongjiang Province, PR China.
J Colloid Interface Sci. 2011 Jun 15;358(2):521-6. doi: 10.1016/j.jcis.2011.03.064. Epub 2011 Mar 23.
Molecular dynamics simulations and free energy perturbation (FEP) were performed for studying the enthalpy-entropy compensation with a series of ionic liquid-type Gemini imidazolium surfactants (ILGIS), with different carbon atoms of the hydrophobic group or the spacer chain length, in aqueous solutions. According to the law of mass action, the thermodynamic properties of micellization in aqueous solutions for ILGIS were discussed. The results show that the solvation free energy changes calculated from the free energy perturbation are close to the Gibbs free energy calculated from the surface tension method and can be used to discriminate the tendency for micellization and predict the thermodynamic properties of ILGIS. The micellization of ILGIS in aqueous solutions is a spontaneous and entropy-driven process. It is enthalpy-entropy compensated, and the enthalpy-entropy compensation plots exhibit an excellent linearity. The compensation temperature was found to be (307±2) K. As the number carbon atoms in the alkyl chains is increased, the tendency and stability of micellization both increase. At spacer length S≤6, with the spacer chain length increasing, the thermodynamic favorability and stability of the micelles decrease. However, if S>6, thermodynamic favorability and stability increase with raising the spacer chain length.
采用分子动力学模拟和自由能微扰（FEP）方法研究了一系列离子液体型Gemini 咪唑啉表面活性剂（ILGIS）在水溶液中的焓熵补偿。根据质量作用定律，讨论了 ILGIS 在水溶液中的胶束化热力学性质。结果表明，从自由能微扰计算得出的溶剂化自由能变化与从表面张力法计算得出的吉布斯自由能接近，可以用来区分胶束化的趋势并预测 ILGIS 的热力学性质。ILGIS 在水溶液中的胶束化是一个自发的熵驱动过程。它是焓熵补偿的，焓熵补偿图表现出极好的线性。补偿温度为（307±2）K。随着烷基链中碳原子数的增加，胶束化的趋势和稳定性都增加。在间隔基长度 S≤6 时，随着间隔基链长的增加，胶束的热力学有利度和稳定性降低。然而，如果 S>6，则随着间隔基链长的增加，热力学有利度和稳定性增加。
