动态光散射研究盐对Gemini表面活性剂网状聚集体的影响

以动态光散射为主要手段研究了盐对羧酸盐Gemini表面活性剂O,O′-双(2-月桂酸钠)-p-二苯氧(记为C12φ2C12)自组织的影响.结果表明盐的加入很容易使C12φ2C12的网状聚集体转变为小(流体力学半径Rh,app约几纳米)和大(Rh,app100 nm)两种尺寸共存的聚集体,1,6-二苯基-1,3,5-己三烯(DPH)探针增溶实验证实小尺寸聚集体为核-壳结构的似球胶束,流变学测量说明大尺寸聚集体可能已经是线型的核-壳胶束.这种行为被归结为初始的网状聚集体不稳定,添加的反离子与C12φ2C12头基结合破坏了网状结构的亲水亲油平衡,促使了它们的转变.盐效应规律表现为MgCl2NaCl、Bu4NBrMe4NBrEt4NBrPr4NBr,这里Bu4NBr不遵循上述静电力顺序的原因是它提供了携带的丁基与C12φ2C12烷烃链疏水相互作用的附加力.

Salt Effects on the Network-Like Aggregates of Gemini Surfactant Studied by Dynamic Light Scattering

The effects of different salts on the self-assembly of the carboxylate Gemini surfactant O,O'-bis (sodium 2-dodecylcarboxylate)-p-dibenzenediol (referred to as C₁₂φ₂C₁₂) were studied using dynamic light scattering measurements. The results showed that the addition of salts induced the transition of the networklike aggregates into two new aggregates with small (hydrodynamic radii R_h,app of several nanometers) and large (R_h,app>100 nm) sizes, which coexisted in solution. A solubilization test using a 1,6-diphenyl-1,3,5-hexatriene (DPH) probe confirmed that the small aggregates were spherical micelles with a core-shell structure. Rheological measurements suggested that the large aggregates were threadlike micelles. The aggregate transition was attributed to the instability of the initially formed network-like aggregates. The added counter-ions associated with the head-groups of C₁₂φ₂C₁₂, which destroyed the hydrophile-lipophile balance and resulted in the aggregate transition. The salt effect followed the order: MgCl₂>NaCl, Bu₄NBr>Me₄NBr>Et₄NBr>Pr₄NBr, where Bu₄NBr is special and not in the order of electrostatic attraction since it provides an additional force through the hydrophobic interaction of its butyls with the alkyl tails of C₁₂φ₂C₁₂.