Bilayers at High pH in the Fatty Acid Soap Systems and the Applications for the Formation of Foams and Emulsions

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• 作者：Wenlong Xu ; Heng Zhang ; Yingping Zhong ; Liwen Jiang ; Mengxin Xu ; Xionglu Zhu ; Jingcheng Hao
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：August 20, 2015
• 年：2015
• 卷：119
• 期：33
• 页码：10760-10767
• 全文大小：462K
• ISSN：1520-5207

文摘

In our previous work, we reported bilayers at high pH in the stearic acid/CsOH/H₂O system,24 which was against the traditional viewpoint that fatty acid (FA) bilayers must be formed at the pK_a of the fatty acid. Herein, the microstructures at high pH of several fatty acid soap systems were investigated systematically. We found that palmitic acid/KOH/H₂O, palmitic acid/CsOH/H₂O, stearic acid/KOH/H₂O, and stearic acid/CsOH/H₂O systems can form bilayers at high pH. The bilayer structure was demonstrated by cryogenic transmission electron microscopy (cryo-TEM) and deuterium nuclear magnetic resonance (²H NMR), and molecular dynamics simulation was used to confirm the formation of bilayers. The influence of fatty acids with different chain lengths (n = 10, 12, 14, 16, and 18) and different counterions including Li⁺, Na⁺, K⁺, Cs⁺, (CH₃)₄N⁺, (C₂H₅)₄N⁺, (C₃H₇)₄N⁺, and (C₄H₉)₄N⁺ on the formation of bilayers was discussed. The stability of foam and emulsification properties were compared between bilayers and micelles, drawing the conclusion that bilayer structures possess a much stronger ability to foam and stronger emulsification properties than micelles do.