Salt Effects on Lamellar Structure of Nonionic Surfactants

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• 作者：Mafumi Hishida ; Yohei Kaneko ; Yasuhisa Yamamura…
• 关键词：Nonionic surfactant ; Lamellar repeat distance ; Monovalent ion ; Role of water structure
• 刊名：Journal of Solution Chemistry
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：45
• 期：11
• 页码：1612-1619
• 全文大小：598 KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Physical Chemistry
  Industrial Chemistry and Chemical Engineering
  Geochemistry
  Oceanography
  Inorganic Chemistry
  Condensed Matter
  
• 出版者：Springer Netherlands
• ISSN：1572-8927
• 卷排序：45

文摘

Effects of monovalent and monatomic salts on lamellar repeat distances d of nonionic surfactants (monomyristolein and \({\mathrm {C_{12}E_{2}}}\)) are investigated using small-angle X-ray diffraction. The lamellar repeat distances (sum of thicknesses of a bilayer and a sandwiched water layer) increase with increasing salt concentration with a strong anion dependence (Br\(^->\) Cl\(^- \)). The increase of the thickness of the water layer is found to dominate the increase in d. Since the anion dependence is inconsistent with the ion dependence of the strength of the primary hydration, we reported previously (Hishida et al. J Chem Phys 142:171101, 2015), the hydration force classically considered is not the origin of the increase in d. This means the increase in d cannot be explained by the existing model of the forces between neutrally charged bilayers. The temperature dependence of d also supports the necessity for a new mechanism of the effect of ions. The new mechanism seems to be related to the water structure beyond the primary hydration water, i.e., the secondary hydration water, which depends on the ion species.