Aqueous Solution Properties of Disulfide Linked Gemini and Cleaved Monomeric Thiol Surfactants

Abstract

Monomeric thiol surfactants, [C_nH_2n+1N(CH₃)₂CH₂CH₂SH]Br, were produced by the cleavage of gemini surfactant containing a disulfide bond in the spacer chain, [C_nH_2n+1N(CH₃)₂CH₂CH₂SSCH₂CH₂N(CH₃)₂C_nH_2n+1]2Br. The disulfide bond was completely reduced by the addition of four times moles of dithiothreitol in water at room temperature. The critical micelle concentrations of monomeric surfactants were significantly increased in comparison with original gemini surfactants. The monomeric thiol surfactants were stable in the presence of dithiothreitol, whereas they returned gradually to their original gemini surfactants within several days due to air oxidation in water without dithiothreitol. The micelle formation induced by the disulfide linkage formation was suggested by the fluorescence intensity ratio of pyrene. The time course of decrease in thiol concentration associated with the recovery of gemini surfactants was confirmed by the absorption spectra utilizing the reactions with 4,4’-dithiopyridine.