Temperature- and pH-Dependent Shattering: Insoluble Fatty Ammonium Phosphate Films at Water鈥揙il Interfaces

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• 作者：Joe Forth ; David J. French ; Andrei V. Gromov ; Stephen King ; Simon Titmuss ; Kathryn M. Lord ; Mike J. Ridout ; Pete J. Wilde ; Paul S. Clegg
• 刊名：Langmuir
• 出版年：2015
• 出版时间：September 1, 2015
• 年：2015
• 卷：31
• 期：34
• 页码：9312-9324
• 全文大小：700K
• ISSN：1520-5827

文摘

We study the films formed by tetradecylamine (TDA) at the water鈥揹odecane interface in the presence of hydrogen phosphate ions. Using Fourier transform infrared spectroscopy (FTIR), interfacial shear rheology, confocal fluorescence microscopy, cryo-scanning electron microscopy (cryo-SEM), and small-angle neutron scattering (SANS), we find that between pH 5 and 8 tetradecylammonium cations bind to hydrogen phosphate anions to form needle-shaped crystallites of tetradecylammonium hydrogen phosphate (TAHP). These crystallites self-assemble into films with a range of morphologies; below pH 7, they form brittle, continuous sheets, and at pH 8, they form lace-like networks that deform plastically under shear. They are also temperature-responsive: when the system is heated, the film thins and its rheological moduli drop. We find that the temperature response is caused by dissolution of the film in to the bulk fluid phases. Finally, we show that these films can be used to stabilize temperature-responsive water-in-oil emulsions with potential applications in controlled release of active molecules.