期刊
JOURNAL OF COLLOID AND INTERFACE SCIENCE
卷 447, 期 -, 页码 173-181出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcis.2014.11.003
关键词
CO2-trigger; Wormlike micelles; Anionic natural surfactant; Viscoelastic surfactant fluids
资金
- Natural Science Foundation of China [21173207, 21273223]
- Science and Technology Department of Sichuan Province [2012NZ0006, 2010JQ0029]
Simple green triggers such as CO2 for switching viscoelastic surfactant solutions between an on and off state without compromising their inherent properties have been a key focus of research in smart soft matter over the past decade. Here we report a CO2-induced anionic wormlike micellar fluid by introducing triethylamine (TEA) into natural anionic surfactant sodium erucate (NaOEr) at a molar ratio (C-NaOEr:C-TEA) Of 3:10. When CO2 is bubbled, pH of the solution decreases from 12.3 to 10.0, and TEA is protonated into a quaternary ammonium salt, which facilitates the growth of micelles as a hydrotrope by screening electrostatic repulsion between the anionic headgroups in NaOEr molecules, resulting in the formation of wormlike micelles and viscoelasticity buildup; upon removal of CO2, the quaternized TEA is deprotonated back into a non-ionic tertiary amine, thus electrostatic repulsion strengthens and the viscoelastic fluid converting it back to the initial low viscosity spherical micellar solution. Such a reversible sphere-to-worm transition could be repeated several cycles without any loss of response to CO2 in the pH range of 12.3-10.0, but when further bubbling excess CO2 to pH < 9.50, the solution transforms into a cloudy dispersion with low viscosity due to the de-neutralization of NaOEr, and this process is irreversible. This study offers a facile way to fabricate smart viscoelastic fluids by incorporating a low-molecular weight CO2-sensitive hydrotrope with conventional long-chain surfactants. (C) 2014 Elsevier Inc. All rights reserved.
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