动态光散射研究盐对Gemini表面活性剂网状聚集体的影响

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

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,app>100 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MgCl2>NaCl、Bu4NBr>Me4NBr>Et4NBr>Pr4NBr,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.

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 C12·2C12） were studied using dynamic light scattering measurements. The results showed that the addition of salts induced the transition of the network-like aggregates into two new aggregates with smal （hydrodynamic radi Rh,app of several nanometers） and large （Rh,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 smal aggregates were spherical micelles with a core-shel structure. Rheological measurements suggested that the large aggregates were threadlike micelles. The aggregate transition was attributed to the instability of the initial y formed network-like aggregates. The added counter-ions associated with the head-groups of C12·2C12, which destroyed the hydrophile-lipophile balance and resulted in the aggregate transition. The salt effect fol owed 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 C12·2C12.