New Insight into the Structure of CTAB Micelles in the Presence of Cyclodextrins, Using Non-Steroidic Anti-Inflammatory Agents -- Nabumetone, Naproxen -- as Fluorescent Probes

The structure of CTAB micelles in the presence of {/content/8mc6tv6jahxb87nq/xxlarge945.gif}-, {/content/8mc6tv6jahxb87nq/xxlarge946.gif}- and hydroxypropyl-{/content/8mc6tv6jahxb87nq/xxlarge946.gif}-cyclodext r in has been investigated by means of conductivity and spectroscopic measurements -- absorption and steady state fluorescence -- using Naproxen, Nabumetone and pyrene as probes. In the presence of the three cyclodextrins, two types of micelles have been detected. The first type is a pure surfactant micelle, while the other is formed by surfactant monomers complexed with cyclodextrins. The presence of cyclodextrins produces a decrease in the cmc of the pure micelle. The second type of micelle is formed at higher cmc* values, 25.6 X 10 M, 27.8 X 10 M and 38.9 X 10 M for {/content/8mc6tv6jahxb87nq/xxlarge945.gif}-, {/content/8mc6tv6jahxb87nq/xxlarge946.gif}-, and HP{/content/8mc6tv6jahxb87nq/xxlarge946.gif}CD respectively. A significant increase in the ionisation degree has been detected. The aggregation number is strongly increased, being 92 ± 3 , 97 ± 3 and 80 ± 2 for for {/content/8mc6tv6jahxb87nq/xxlarge945.gif}-, {/content/8mc6tv6jahxb87nq/xxlarge946.gif}-, and HP{/content/8mc6tv6jahxb87nq/xxlarge946.gif}CD respectively. The polarity of this micelle decreases, indicating that it becomes tighter and its hydrophobic region becomes less polar.