Muzzalupo Rita, Gente Giacomo, La Mesa Camillo, Caponetti Eugenio, Chillura-Martino Delia, Pedone Lucia, Saladino Maria Luisa
Dipartimento Scienze Farmaceutiche, Università della Calabria, Via P. Bucci, Arcavacata di Rende 87030, Italy.
Langmuir. 2006 Jul 4;22(14):6001-9. doi: 10.1021/la052863h.
Mixtures composed of water, sodium dodecyl sulfate (SDS), and a bolaform surfactant with two aza-crown ethers as polar headgroups (termed Bola C-16) were investigated by modulating the mole ratios between the components. The two surfactants have ionic and nonionic, but ionizable, headgroups, respectively. The ionization is due to the complexation of alkali ions by the aza-crown ether unit(s). Structural, thermodynamic, and transport properties of the above mixtures were investigated. Results from surface tension, translational self-diffusion, and small angle neutron scattering (SANS) are reported and discussed. Interactions between the two surfactants to form mixed micelles result in a combination of electrostatic and hydrophobic contributions. These effects are reflected in the size and shape of the aggregates as well as in transport properties. The translational diffusion of the components in mixed micelles, in particular, depends on the Bola C-16/SDS mole ratio. Nonideality of mixing of the two components was inferred from the dependence of the critical micelle concentration, cmc, on the mole fraction of Bola C-16. This behavior is also reflected in surface adsorption and in the area per polar headgroup at the air-water interface. SANS data analysis for the pure components gives results in good agreement with previous findings. An analysis of data relative to mixed systems allows us to compute some structural parameters of the mixed aggregates. The dependence of aggregation numbers, nu(T), on the Bola C-16/SDS mole ratio displays a maximum that depends on the overall surfactant content and is rationalized in terms of the nonideality of mixing. Aggregates grow perpendicularly to the major rotation axis, as formerly observed in the Bola C-16 system, and become progressively ellipsoidal in shape.
通过调节各组分之间的摩尔比，对由水、十二烷基硫酸钠（SDS）和一种带有两个氮杂冠醚作为极性头基的bola型表面活性剂（称为Bola C-16）组成的混合物进行了研究。这两种表面活性剂分别具有离子型和非离子型但可电离的头基。电离是由于氮杂冠醚单元与碱金属离子的络合作用。研究了上述混合物的结构、热力学和传输性质。报道并讨论了表面张力、平移自扩散和小角中子散射（SANS）的结果。两种表面活性剂之间形成混合胶束的相互作用导致了静电和疏水作用的结合。这些效应反映在聚集体的大小和形状以及传输性质上。特别是，混合胶束中各组分的平移扩散取决于Bola C-16/SDS摩尔比。从临界胶束浓度cmc对Bola C-16摩尔分数的依赖性推断出两种组分混合的非理想性。这种行为也反映在表面吸附和空气-水界面处每个极性头基的面积上。对纯组分的SANS数据分析结果与先前的发现吻合良好。对混合体系相关数据的分析使我们能够计算混合聚集体的一些结构参数。聚集数nu(T)对Bola C-16/SDS摩尔比的依赖性呈现出一个最大值，该最大值取决于表面活性剂的总含量，并根据混合的非理想性进行了合理化解释。聚集体垂直于主旋转轴生长，如先前在Bola C-16体系中观察到的那样，并且形状逐渐变为椭圆形。
