Transition from Nanotubes to Micelles with Increasing Concentration in Dilute Aqueous Solution of Potassium N-Acyl Phenylalaninate

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• 作者：Akio Ohta ; Radostin Danev ; Kuniaki Nagayama ; Toshimitsu Mita ; Tsuyoshi Asakawa ; Shigeyoshi Miyagishi
• 刊名：Langmuir
• 出版年：2006
• 出版时间：September 26, 2006
• 年：2006
• 卷：22
• 期：20
• 页码：8472 - 8477
• 全文大小：494K
• 年卷期：v.22,no.20(September 26, 2006)
• ISSN：1520-5827

文摘

An aggregation behavior of potassium N-acyl phenylalaninate in dilute aqueous solution was investigated. It wasfound that this surfactant formed large aggregates at lower concentrations, which were then transformed to micellesat higher concentrations. Fluorescence intensity measurements using a probe were used to examine the effects of alkaliconcentration, acyl chain length, and solvent isotope on the aggregation behavior. The influence of the alkali concentrationsuggested that formation of an acid-soap dimer brought about the construction of the large particles at very diluteconcentrations. Increases in both the acyl chain length and replacement of H₂O with D₂O resulted in stronger hydrophobicinteractions; consequently, the large aggregate formation was enhanced. This aggregation behavior has not beenobserved when racemic modification of N-acyl phenylalaninate has taken place. By using cryo-transmission electronmicroscopy (TEM) with a Zernike differential contrast phase plate, it was found that the large aggregates were tubeswith bilayer structures, which were then transformed into spherical micelles via threadlike micelles with increasingconcentration due to a drastic increase in the concentration of ionic species in the aggregate.