Micelle-to-vesicle transition induced by β-cyclodextrin in mixed catanionic surfactant solutions

• Aggregate transition was successfully achieved in catanionic surfactant solutions.
• Through the addition of β-CD, micelles can be transformed into vesicles.
• Association constants were investigated to show the ability of inclusion complexation of β-CD to surfactants.

Micelle-to-vesicle aggregate transition is investigated in this work through the addition of β-cyclodextrin 1(β-CD) in mixed catanionic surfactant aqueous solutions. The catanionic system is composed of 1-hexadecyl-3-methylimidazolium chloride (C16mimCl) and sodium oleate (NaOle) which are cationic surfactant and anionic surfactant, respectively. The mixed surfactant solutions can self −assemble into micelles, which are studied by dynamic light scattering measurements and the calculation of molecular interaction parameter. The inclusion complexation of β-CD to C16mimCl-NaOle surfactants is studied by surface tension measurements and the calculation of association constants. The dynamic light scattering (DLS), rheological measurements, freeze-fracture transmission electron microscopy(FF-TEM)were conducted to indicate that micelles can transform into vesicles with the addition of β-CD. Finally, the transformation mechanism is proposed. The main reason for micelle-to-vesicle aggregate transition is the inclusion complexation of β-CD to surfactants and it will alter the composition of mixed C16mimCl-NaOle surfactant systems which should be responsible for the phase behavior.

Micelle-to-vesicle aggregate transition induced by β-CD in catanionic surfactant solutions is investigated in this work. At first, the solutions are transparent and water-like which are proved to be micelles in mixed systems. After the appropriate addition of β-CD, the hydrophobic chains of surfactants will be included in the cavity of β-CD which will increase the critical packing parameter. The association constant value of NaOle is larger than C16mimCl. The NaOle is easier included by β-CD. Due to the formation of inclusion complexes and the increased critical packing parameter, the vesicles are formed.Figure optionsDownload as PowerPoint slide