胶束间的相互作用和表面活性剂溶液的粘弹性：SANS和SAXS的互补使用,Langmuir

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胶束间的相互作用和表面活性剂溶液的粘弹性：SANS和SAXS的互补使用
Langmuir ( IF 3.7 ) Pub Date : 2017-02-28 00:00:00 , DOI: 10.1021/acs.langmuir.6b04466
Viviane Lutz-Bueno ₁ , Marianne Liebi , Joachim Kohlbrecher , Peter Fischer ₁

Affiliation

在离子型表面活性剂胶束中，表面活性剂单体，其抗衡离子和添加剂的不同部分之间的基本相互作用是调节分子自组装和增强粘弹性的基础。在这里，我们研究了将水杨酸钠（NaSal）添加到十六烷基三甲基氯化铵和溴化物（CTAC和CTAB）以及1-十六烷基吡啶鎓氯化物和溴化物（CPyCl和CPyBr），它们具有不同的抗衡离子和头基结构，但疏水尾部相同。小角度中子散射（SANS）（用于探测原子核之间的差异）和X射线SAXS（用于探测电子密度的差异）获得了不同的对比度。如果结合起来，这种对比使我们可以定义特定的胶束内长度尺度和胶束间相互作用。_2个O）和胶束核心中的烃类尾巴（氢），并且SAXS可以进入极性壳的内部结构，因为与溶剂和胶束核心相比，头基，抗衡离子和渗透的盐具有更高的电子密度。基于结构因子和形状因子对胶束聚集体形态的依赖性，讨论了数密度，胶束间距离，聚集数以及胶束间/胶内排斥。因此，我们证实可以通过改变头基的柔性和大小以及其抗衡离子的离子解离速率来调节胶束的生长。此外，我们表明，抗衡离子结合对粘弹性的发展甚至比表面活性剂分子的头基结构更为重要。这是一个令人惊讶的发现，

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Intermicellar Interactions and the Viscoelasticity of Surfactant Solutions: Complementary Use of SANS and SAXS

In ionic surfactant micelles, basic interactions among distinct parts of surfactant monomers, their counterion, and additives are fundamental to tuning molecular self-assembly and enhancing viscoelasticity. Here, we investigate the addition of sodium salicylate (NaSal) to hexadecyltrimethylammonium chloride and bromide (CTAC and CTAB) and 1-hexadecylpyridinium chloride and bromide (CPyCl and CPyBr), which have distinct counterions and headgroup structures but the same hydrophobic tail. Different contrasts are obtained from small-angle neutron scattering (SANS), which probes differences between the nucleus of atoms, and X-rays SAXS, which probes differences in electron density. If combined, this contrast allows us to define specific intramicellar length scales and intermicellar interactions. SANS signals are sensitive to the contrast between the solvent (D₂O) and the hydrocarbonic tails in the micellar core (hydrogen), and SAXS can access the inner structure of the polar shell because the headgroups, counterions, and penetrated salt have higher electron densities compared to the solvent and to the micellar core. The number density, intermicellar distances, aggregation number, and inter/intramicellar repulsions are discussed on the basis of the dependence of the structure factor and form factor on the micellar aggregate morphology. Therefore, we confirm that micellar growth can be tuned by variations in the flexibility and size of the the headgroup as well as the ionic dissociation rate of its counterion. Additionally, we show that the counterion binding is even more significant to the development of viscoelasticity than the headgroup structure of a surfactant molecule. This is a surprising finding, showing the importance of electrostatic charges in the self-assembly process of ionic surfactant molecules.

更新日期：2017-02-28

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