Self-Assembled Networks Highly Responsive to Hydrocarbons

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• 作者：Vyacheslav S. Molchanov ; Olga E. Philippova ; Alexei R. Khokhlov ; Yuri A. Kovalev ; Alexander I. Kuklin
• 刊名：Langmuir
• 出版年：2007
• 出版时间：January 2, 2007
• 年：2007
• 卷：23
• 期：1
• 页码：105 - 111
• 全文大小：146K
• 年卷期：v.23,no.1(January 2, 2007)
• ISSN：1520-5827

文摘

Rheological studies were performed with aqueous salt solutions of anionic surfactant potassium oleate and itsmixtures with hydrophobically modified polyacrylamide. Semidilute solutions of the surfactant in the presence of salt(KCl) demonstrate viscoelastic properties due to the formation of a transient network of entangled wormlike micelles.These systems are highly responsive to hydrocarbons: the addition of n-heptane or n-dodecane reduces the viscosityof solutions by up to 4 to 5 orders of magnitude, thus inducing the transition of a gellike system to a fluid one. Itis the transformation of cylindrical surfactant micelles into spherical ones upon absorption of hydrocarbon that disruptsthe network. The addition of a small amount (0.5 wt %) of associating polymer leads to up to a 5000-fold increasein the zero-shear viscosity and enhances the susceptibility to hydrocarbons. SANS data show that independently ofthe presence of polymer the radius of wormlike micelles is roughly equal to the length of a surfactant molecule, whereasthe radius of spheres formed upon the absorption of hydrocarbon is 2-2.5-fold higher. A possible structure of thespherical micelles is discussed.