Synergistic Formation and Stabilization of Oil-in-Water Emulsions by a Weakly Interacting Mixture of Zwitterionic Surfactant and Silica Nanoparticles
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- 作者：Andrew J. Worthen ; Lynn M. Foster ; Jiannan Dong ; Jonathan A. Bollinger ; Adam H. Peterman ; Lucinda E. Pastora ; Steven L. Bryant ; Thomas M. Truskett ; Christopher W. Bielawski ; Keith P. Johnston
- 刊名：Langmuir
- 出版年：2014
- 出版时间：February 4, 2014
- 年：2014
- 卷：30
- 期：4
- 页码：984-994
- 全文大小：555K
- ISSN：1520-5827
文摘
Oil-in-water emulsions were formed and stabilized at low amphiphile concentrations by combining hydrophilic nanoparticles (NPs) (i.e., bare colloidal silica) with a weakly interacting zwitterionic surfactant, caprylamidopropyl betaine, to generate a high hydrophilic鈥搇ipophilic balance. The weak interaction of the NPs with surfactant was quantified with contact angle measurements. Emulsions were characterized by static light scattering to determine the droplet size distributions, optical photography to quantify phase separation due to creaming, and both optical and electron microscopy to determine emulsion microstructure. The NPs and surfactant acted synergistically to produce finer emulsions with a greater stability to coalescence relative to the behavior with either NPs or surfactant alone. As a consequence of the weak adsorption of the highly hydrophilic surfactant on the anionic NPs along with the high critical micelle concentration, an unusually large surfactant concentration was available to adsorb at the oil鈥搘ater interface and lower the interfacial tension. The synergy for emulsion formation and stabilization for the two amphiphiles was even greater in the case of a high-salinity synthetic seawater aqueous phase. Here, higher NP adsorption at the oil鈥搘ater interface was caused by electrostatic screening of interactions between (1) NPs and the anionic oil鈥搘ater interface and (2) between the NPs. This greater adsorption as well as partial flocculation of the NPs provided a more efficient barrier to droplet coalescence.