Catanionic surfactant systems—thermodynamic and structural conditions revisited
Catanionic surfactant systems—thermodynamic and structural conditions revisited
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DOI：
10.1007/s00396-015-3739-9
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发表时间：
2015-09
影响因子：
2.4
通讯作者：
Leonardo Chiappisi;H. Yalcinkaya;V. Gopalakrishnan;M. Gradzielski;T. Zemb
中科院分区：
文献类型：
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作者：
Leonardo Chiappisi;H. Yalcinkaya;V. Gopalakrishnan;M. Gradzielski;T. Zemb
在这项工作中，我们简要回顾了有关阴阳离子表面活性剂系统的当前知识状况，重点是基于此类系统的分子构建以及控制其两亲单层和双层的静电相互作用的详细理解。这里特别相关的是带相反电荷的配偶体的疏水性程度，其范围可以从仅具有或多或少疏水性抗衡离子直到具有相反电荷的真正表面活性剂。基于此讨论，我们随后研究了基于十六烷基三甲基铵 (CTA) 与作为带相反电荷的表面活性剂的月桂酸盐 (L) 或作为强疏水性抗衡离子的萘磺酸盐 (NS) 相结合的不同系统。研究了两种系统，研究了通过组合两种两亲盐而存在盐的情况，以及由于氢氧化物与酸的组合而产生的无盐情况。通过小角中子散射 (SANS) 和光散射获得相行为以及介观结构，从而可以辨别蠕虫状胶束和囊泡的形成。然后通过流变测量进一步证实了它们的存在，特别是法向力可以区分两种类型的聚集体，并且流变控制是此类系统的关键特性。此外，这些系统中的热力学条件是通过差示扫描量热法（DSC）测定的。基于这些结果，对这些系统中的分子条件所形成的结构及其宏观特性提出了一致的理解。
In this work, we review shortly the current state of knowledge about catanionic surfactant systems with a focus on the detailed understanding based on the molecular buildup of such systems and of the electrostatic interaction that controls their amphiphilic monolayer and bilayer. Particularly relevant here is the extent of hydrophobicity of the oppositely charged partners, which can range from just having a more or less hydrophobic counterion until a real surfactant of opposite charge. Based on this discussion, we then investigate different systems based on cetyltrimethylammonium (CTA) combined with either laurate (L) as an oppositely charged surfactant or naphthalenesulfonate (NS) as a strongly hydrophobic counterion. Both systems were studied for the case of having salt present by combining the two amphiphilic salts but also the salt-free situation which arises from combining the hydroxide with the acid. The phase behavior was determined as well as the mesoscopic structures present, as obtained by small-angle neutron scattering (SANS) and light scattering, which allow to discern formation of wormlike micelles and vesicles. Their presence was then further confirmed by rheological measurements, where in particular normal forces allow to distinguish the two types of aggregates, and control of rheology is a key property in such systems. In addition, the thermodynamic conditions in these systems were determined by means of differential scanning calorimetry (DSC). Based on these results, a consistent understanding of the formed structures and their macroscopic properties that arise from the molecular conditions in these systems is presented.