Bilayers and wormlike micelles at high pH in fatty acid soap systems

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• 作者：Wenlong Xu ; Huizhong Liu ; Aixin Song ; Jingcheng Hao ; ^{jhao@sdu.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Fatty acids ; Counterions ; Wormlike micelles ; pH ; Regulating effect
• 刊名：Journal of Colloid and Interface Science
• 出版年：2016
• 出版时间：1 March 2016
• 年：2016
• 卷：465
• 期：Complete
• 页码：304-310
• 全文大小：1491 K

文摘

Bilayers at high pH in the fatty acid systems of palmitic acid/KOH/H₂O, palmitic acid/CsOH/H₂O, stearic acid/KOH/H₂O and stearic acid/CsOH/H₂O can form spontaneously (Xu et al., 2014, 2015). In this work, the bilayers can still be observed at 25 °C with an increase of the concentration of fatty acids. We found that wormlike micelles can also be prepared in the fatty acid soap systems at high pH, even though the temperature was increased to be 50 °C. The viscoelasticity, apparent viscosity, yield stress of the bilayers were determined by the rheological measurements. Wormlike micelles were identified by cryogenic transmission electron microscopy (cryo-TEM) and emphasized by the rheological characterizations, which are in accordance with the Maxwell fluids with good fit of Cole–Cole plots. The phase transition temperature was determined by differential scanning calorimetry (DSC) and the transition process was recorded. The regulating role of counterions of fatty acids were discussed by (CH₃)₄N⁺, (C₂H₅)₄N⁺, (C₃H₇)₄N⁺, and (C₄H₉)₄N⁺ as comparison, concluding that counterions with appropriate hydrated radius were the vital factor in the formation wormlike micelles.