H NMR study on solubilization of aromatic solutes in gemini cationic surfactant micelles
The 1HNMR spectra of gemini cationic surfactant 1,3-Propane diaminium N,N-didodecyl-2-hydrxyl-N,N,N′N′tetramethyl- dichloride (ClC12H25-(CH3)3 N-CH2CH(OH) CH2N(CH3)2 C12H25 Cl), abbreviated to GC12NCl solutions were determined in the presence of toluene, phenyl ethane, benzyl alcohol, or 2-phenylethanol. Based on observations, probable solubilization sites of the substrate molecule within the micelles are discussed. The examined results indicate that the polarity of aromatic solutes affects their solubilization site in the micelle solution. The methylene in long chain of GC12NCl shows a single signal in the presence of toluene and phenyl ethane, however, when benzyl alcohol or 2-phenylethanol is in existence, the peak of ethylenes in long chain Gemini surfactant splits into an upfield signal and a downfield signal in the solubilization system with enhancement of molar ratio of aromatic solutes to the sufactant. The addition of benzyl alcohol and 2-phenylethanol causes a downfield shift of the methyl signal, the other signal were up field shifted by the addition of the phenyl derivatives. From the dependence of chemical shifts of GC12NCl on solubilizate concentration, it is ascertained that at low solubilizate contents the aromatic solutes are solubilized by adsorption at the micelle-water interface. With further addition of aromatic solutes, the solubilization site of the solubilizate varied gradually from the mantle of the surfactant micelle to its inner core.
Wei, XL; Yin, BL; Liu, J; Sun, DZ; Li, GZ
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