Jestin Jacques, Simon Sébastien, Zupancic Lina, Barré Loïc
Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif sur Yvette Cedex, France.
Langmuir. 2007 Oct 9;23(21):10471-8. doi: 10.1021/la701193f. Epub 2007 Sep 15.
We have developed a specific protocol to study with SANS measurements, the structure of the interfacial film layer in water-in-oil emulsions stabilized by asphaltene. Using the contrast matching technique available for neutron scattering, we have access to both the composition and the quantity of interface. The results obtained give us a view of the asphaltene aggregates in the interfacial film, which are structured as a monolayer and show a direct correlation between the size of asphaltene aggregates in solution and the thickness of the film layer. The organization of the interface has been studied as a function of several parameters such as the quantity of resins, i.e., the size of aggregates, the pH of the aqueous phase, and the aging time of the emulsions and the consequences of these variations on the macroscopic stability of these emulsions. We show that the key parameter for the stability is the inter-asphaltene aggregate interaction inside the film layer. Changing the attractive/repulsive balance between the aggregates in the film at the microscopic scale, by changing the aggregate's size or the aggregate's ionization, has a direct incidence on the quantity of water recovered after centrifugation: the stronger the attraction between aggregates in the film, the more stable the emulsion is.
我们已经开发出一种特定的方案，用于通过小角中子散射（SANS）测量来研究由沥青质稳定的油包水乳液中界面膜层的结构。利用中子散射可用的对比匹配技术，我们能够获取界面的组成和数量。所获得的结果让我们了解到界面膜中沥青质聚集体的情况，它们构成单层结构，并且显示出溶液中沥青质聚集体的大小与膜层厚度之间存在直接关联。已经研究了界面的组织与几个参数的关系，例如树脂的量，即聚集体的大小、水相的pH值、乳液的老化时间，以及这些变化对这些乳液宏观稳定性的影响。我们表明，稳定性的关键参数是膜层内沥青质聚集体之间的相互作用。通过改变聚集体的大小或聚集体的电离程度，在微观尺度上改变膜中聚集体之间的吸引/排斥平衡，会直接影响离心后回收的水量：膜中聚集体之间的吸引力越强，乳液就越稳定。
