Micelle–Vesicle Transition by Cleavage of Disulfide Spacer Chain for Gemini Surfactant in Didodecyldimethylammonium Chloride Aqueous Solutions

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We examined the “micelle-vesicle transition” through the mixing effect of single–tailed thiol surfactants produced by the cleavage of gemini surfactants, [C₁₂H₂₅N(CH₃)₂CH₂CH₂SSCH₂CH₂N(CH₃)₂C₁₂H₂₅] 2Cl (C₁₂SSC₁₂), which have a disulfide bond in the spacer chain. Phase diagrams of C₁₂H₂₅N(CH₃)₂CH₂CH₂SHCl-didodecyldimethylammonium chloride (C₁₂SH-DDAC) and C₁₂SSC₁₂-DDAC were determined by conductivity and pyrene fluorescence probe methods. The aggregate diameters were evaluated by dynamic light scattering (DLS). The critical vesicle concentration (CVC) was confirmed by the abrupt increase in the intensity of light scattering with excitation at 335 nm. Vesicle formation was confined to the DDAC-rich region of the C₁₂SSC₁₂-DDAC system, while the vesicle formation region for the C₁₂SH-DDAC system spread out with the addition of dithiothreitol (DTT) to C₁₂SSC₁₂-DDAC. This implies that single–tailed surfactants can induce a more favorable environment for molecular packing of the vesicular surface. The micelle-vesicle transition occurs with disulfide spacer chain cleavage of gemini surfactants at a particular specific concentration range.