Effect of Salts on the Phase Behavior and the Stability of Nano-Emulsions with Rapeseed Oil and an Extended Surfactant

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• 作者：Angelika Klaus ; Gordon J. T. Tiddy ; Conxita Solans ; Agnes Harrar ; Didier Touraud ; Werner Kunz
• 刊名：Langmuir
• 出版年：2012
• 出版时间：June 5, 2012
• 年：2012
• 卷：28
• 期：22
• 页码：8318-8328
• 全文大小：559K
• 年卷期：v.28,no.22(June 5, 2012)
• ISSN：1520-5827

文摘

For many decades, the solubilization of long-chain triglycerides in water has been a challenge. A new class of amphiphiles has been created to overcome this solubilization problem. The so-called 鈥渆xtended鈥?surfactants contain a hydrophilic鈥搇ipophilic linker to reduce the contrast between the surfactant鈥搘ater and surfactant鈥搊il interfaces. In the present contribution, the effects of different anions and cations on the phase behavior of a mixture containing an extended surfactant (X-AES), a hydrotrope (sodium xylene sulfonate, SXS), water, and rapeseed oil were determined as a function of temperature. Nanoemulsions were obtained and characterized by conductivity measurements, light scattering, and optical microscopy. All salting-out salts show a transition from a clear region (O/W nanoemulsion), to a lamellar liquid crystalline phase region, a clear phase (bicontinuous L₃), and again to a lamellar liquid crystalline phase region with increasing temperature. For the phase diagrams with NaSCN and Na₂SO₄, only one clear region (O/W nanoemulsion) was observed, which turns into a lamellar phase region at elevated temperatures. Furthermore, the stability of the nanoemulsions was investigated by time-dependent measurements: the visual observation of phase separation, droplet size by dynamic light scattering (DLS), and optical microscopy. The mechanism of the different phase transitions is also discussed.