Hierrezuelo J M, Aguiar J, Ruiz C Carnero
Grupo de Fluidos Estructurados y Sistemas Anfifílicos, Departamento de Física Aplicada II, Escuela Universitaria Politécnica, Universidad de Málaga, Campus de El Ejido, 29013 Málaga, Spain.
Langmuir. 2004 Nov 23;20(24):10419-26. doi: 10.1021/la048278i.
The mixed micellization between the nonionic surfactant decanoyl-N-methylglucamide (MEGA-10) and the common sodium dodecyl sulfate (SDS) in aqueous solutions of 0.1 M NaCl was investigated by the fluorescence probe method. The critical micelle concentrations were determined by the pyrene 1:3 ratio method. The experimental data are discussed in light of two mixing thermodynamic models within the framework of the pseudophase separation model, including the conventional regular solution theory and a recent treatment proposed by Maeda (J. Phys. Chem. B 2004, 108, 6043). This last approach provides a more appropriate description of the mixed system, particularly in two aspects: the nature of the interactions responsible for the stability of the mixed micelle and the behavior of the excess free energy per monomer of the system. By using the static quenching method, the mean micellar aggregation numbers of mixed micelles in the whole range of compositions were obtained. It was found that the micellar aggregation number initially increases with the content of the ionic component, then remains roughly constant, and, finally, decreases slightly for high content of this component. This behavior was analyzed taking into account the effects produced by the presence of the charged headgroups of sodium dodecyl sulfate, as this component increases its participation in the mixed micelle. The micropolarity of the mixed micelles was studied by the pyrene 1:3 ratio index. It was observed that the increasing participation of the ionic component induces the formation of micelles with a more dehydrated structure. Data of micellar microviscosity were obtained by using different methods, including fluorescence intensity measurements of Auramine O and steady-state fluorescence anisotropy of rhodamine B and diphenylbutadiene. The results obtained from these experiments are in good agreement and suggest the formation of mixed micelles with a less ordered structure as the content of SDS increases.
采用荧光探针法研究了非离子表面活性剂癸酰基 - N - 甲基葡糖酰胺（MEGA - 10）与常见的十二烷基硫酸钠（SDS）在0.1 M NaCl水溶液中的混合胶束化过程。通过芘1:3比例法测定临界胶束浓度。在假相分离模型框架内，依据两种混合热力学模型对实验数据进行了讨论，这两种模型包括传统的正规溶液理论以及前田提出的最新处理方法（《物理化学杂志B》2004年，108卷，6043页）。后一种方法对混合体系给出了更恰当的描述，尤其在两个方面：负责混合胶束稳定性的相互作用的性质以及体系中每个单体的过量自由能的行为。采用静态猝灭法，得到了整个组成范围内混合胶束的平均胶束聚集数。发现胶束聚集数最初随离子组分含量增加而增大，然后大致保持恒定，最后在该组分含量较高时略有下降。考虑到十二烷基硫酸钠带电头基的存在所产生的影响，对这种行为进行了分析，因为该组分在混合胶束中的参与度增加。通过芘1:3比例指数研究了混合胶束的微极性。观察到离子组分参与度的增加会诱导形成结构更脱水的胶束。通过使用不同方法获得了胶束微粘度数据，包括金胺O的荧光强度测量以及罗丹明B和二苯基丁二烯的稳态荧光各向异性测量。这些实验得到的结果吻合良好，表明随着SDS含量增加，会形成结构不太有序的混合胶束。
