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

Micelle-to-vesicle aggregate transition is investigated in this work through the addition of beta-cyclodextrin (1)(beta-CD) in mixed catanionic surfactant aqueous solutions. The catanionic system is composed of 1 hexadecy-1-3-methylimidazolium chloride (C(16)mimCl) 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 beta-CD to C(16)mimCl-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 micros copy(FF-TEM)were conducted to indicate that micelles can transform into vesicles with the addition of beta-CD. Finally, the transformation mechanism is proposed. The main reason for micelle-to-vesicle aggregate transition is the inclusion complexation of beta-CD to surfactants and it will alter the composition of mixed C(16)mimCl-NaOle surfactant systems which should be responsible for the phase behavior. (C) 2016 Elsevier B.V. All rights reserved.