Lu Ting, Huang Jianbin, Liang Dehai
College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic of China.
Langmuir. 2008 Mar 4;24(5):1740-4. doi: 10.1021/la702832v. Epub 2008 Jan 18.
A cationic gemini surfactant, dodecanediyl-1,12-bis(dodecyldiethylammonium bromide) (C12C12C12(Et)), in aqueous solutions with varying NaBr concentration was studied by dynamic light scattering (DLS). As a comparison, its single-chained counterpart, dodecyl triethylammonium bromide (DTEAB), was also investigated under the same conditions. Similar to the case of a polyelectrolyte, C12C12C12(Et) underwent a typical "ordinary-to-extraordinary (o-e) transition" with decreasing salt concentration to zero. At higher salt concentration, a single relaxation mode, corresponding to the diffusion of regular micelles, was observed. While in the "extraordinary regime", DLS detected two characteristic relaxation modes with the values of the diffusion coefficient being different by at least 2 orders. The fast mode was consistent with the polyion-small ion coupled-mode theories, as well as the direct polyion-polyion repulsion interactions. Because the slow mode disappeared at elevated salt concentrations and generated negligible scattered intensity, we attributed it to multimacroion domains.
通过动态光散射（DLS）研究了一种阳离子双子表面活性剂十二烷二基-1,12-双（十二烷基二乙铵溴化物）（C12C12C12(Et)）在不同溴化钠浓度的水溶液中的情况。作为对比，在相同条件下也研究了其单链类似物十二烷基三乙铵溴化物（DTEAB）。与聚电解质的情况类似，随着盐浓度降低至零，C12C12C12(Et)经历了典型的“普通到非凡（o-e）转变”。在较高盐浓度下，观察到对应于常规胶束扩散的单一弛豫模式。而在“非凡区域”，DLS检测到两种特征弛豫模式，其扩散系数值相差至少2个数量级。快速模式与聚离子-小离子耦合模式理论以及直接的聚离子-聚离子排斥相互作用一致。由于慢速模式在盐浓度升高时消失且产生的散射强度可忽略不计，我们将其归因于多宏观离子域。
