ŠArac Bojan, Bešter-Rogač Marija
Acta Chim Slov. 2020 Sep;67(3):977-984.
The micellization of sodium dodecyl sulfate (SDS) in water and aqueous solutions of NaCl (0.1 M) and three ionic liquids (IL, 0.01 M) with different side-chain length, i.e. 1,3-dimethylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, and 1-butyl-3-methylimidazolium chloride was investigated in the temperature range from 288.15 to 328.15 K using isothermal titration calorimetry (ITC). Thermodynamics of micellization was studied by the fitting of the mass-action model to the ITC data. The micellization of SDS in all the studied systems is an entropy-driven at lower temperatures and an enthalpy-driven at higher temperatures. It was also found that with the increasing nonpolar character of IL the interactions between the SDS should be stronger leading to more negative Gibbs free energy and enthalpy of micellization. To obtain information about the micellar charge, the conductivity and zeta-potential measurements were performed at 298.15 K. It is assumed that the charge screening between negative sulfate heads is more efficient in the presence of ILs due to their possible incorporation into the micellar structure reflecting in less negative zeta-potential of micelles comparing to SDS in water and consequently higher degrees of micelle ionization due to the larger portion of sodium ions in solution.
使用等温滴定量热法（ITC）在288.15至328.15 K的温度范围内，研究了十二烷基硫酸钠（SDS）在水、0.1 M NaCl水溶液以及三种具有不同侧链长度的离子液体（IL，0.01 M）中的胶束化情况，这三种离子液体分别是1,3 - 二甲基咪唑鎓氯化物、1 - 乙基 - 3 - 甲基咪唑鎓氯化物和1 - 丁基 - 3 - 甲基咪唑鎓氯化物。通过将质量作用模型拟合到ITC数据来研究胶束化的热力学。SDS在所有研究体系中的胶束化在较低温度下是熵驱动的，在较高温度下是焓驱动的。还发现随着离子液体非极性特征的增加，SDS之间的相互作用应该更强，导致胶束化的吉布斯自由能和焓更负。为了获得有关胶束电荷的信息，在298.15 K下进行了电导率和zeta电位测量。据推测，由于离子液体可能掺入胶束结构中，在其存在下硫酸根负离子头之间的电荷屏蔽更有效，这反映在与水中的SDS相比，胶束的zeta电位负性更小，并且由于溶液中钠离子比例更大，胶束电离程度更高。
