Ion Exchange in Catanionic Mixtures: From Ion Pair Amphiphiles to Surfactant Mixtures
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- 作者：Eva Maurer ; Luc Belloni ; Thomas Zemb ; David Carriè ; re
- 刊名：Langmuir
- 出版年：2007
- 出版时间：June 5, 2007
- 年：2007
- 卷：23
- 期：12
- 页码：6554 - 6560
- 全文大小：104K
- 年卷期：v.23,no.12(June 5, 2007)
- ISSN：1520-5827
文摘
We have studied concentrated equimolar mixtures of tetradecanoic acid (myristic acid, C13COOH) andhexadecyltrimethylammonium hydroxide (CTAOH) in which the OH- counterions are gradually exchanged by otheranions (Cl-, Br-, CH3COO-, CH3-(C6H4)-SO3-). We demonstrate that the stability of a L
phase can be achievedat equimolarity between both surfactants, provided that the phase contains also a sufficient number of anions exchangedwith OH-. In the absence of exchange (equimolar mixture of C13COOH and CTAOH), a three-dimensional crystallineLc phase is produced. As the OH- ions are replaced by other ions, a swollen L lamellar phase appears, first incoexistence with the Lc (D* = 400 Å) and then in coexistence with a dilute phase only (D* = 215 Å). In the latterregime, the repeating distance depends very little on the exchange ratio, but rather on the nature of the counterion.If too many OH- ions are exchanged, the L phase becomes unstable again. A Poisson-Boltzmann model with chargeregulation computed for a closed system predicts qualitatively the existence of this narrow domain of stability forthe L phase.
phase can be achievedat equimolarity between both surfactants, provided that the phase contains also a sufficient number of anions exchangedwith OH-. In the absence of exchange (equimolar mixture of C13COOH and CTAOH), a three-dimensional crystallineLc phase is produced. As the OH- ions are replaced by other ions, a swollen L lamellar phase appears, first incoexistence with the Lc (D* = 400 Å) and then in coexistence with a dilute phase only (D* = 215 Å). In the latterregime, the repeating distance depends very little on the exchange ratio, but rather on the nature of the counterion.If too many OH- ions are exchanged, the L phase becomes unstable again. A Poisson-Boltzmann model with chargeregulation computed for a closed system predicts qualitatively the existence of this narrow domain of stability forthe L phase.