pH-Responsive Emulsions with Supramolecularly Assembled Shells
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© 2018 American Chemical Society. Herein, we describe a novel and simple pH-switchable oil-in-water emulsion system prepared by intermolecular assembly of an amino-amide and a trace amount of citric acid. The resultant supramolecular complex, which demonstrated highly pH-responsive properties, was characterized with various techniques, including attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, zeta potential, dynamic light scattering (DLS), surface tension, and interfacial tension. The switchable cyles between emulsification-demulsification states via adjusting the pH through the addition of acid or base were demonstrated with several types of oils. While emulsion was very stable at a pH of 2.2; a rapid phase separation was observed at and above pH of 5.5. Upon adjusting pH back to 2.2, stable emulsion could be re-assembled via dynamic intermolecular interactions. Such pH-triggered emulsification and demulsification cycles could be switched at least five times. The intriguing properties of these pH-switchable emulsions indicate their potential in several industrial applications such as enhanced oil recovery and cosmetics industry.
author list (cited authors)
Hao, L. i., Yegin, C., Chen, I., Oh, J. K., Liu, S., Scholar, E., ... Jiang, B.