title: Reversible switching of a micelle-to-vesicle transition by compressed CO2.
abstract: The study of the micelle-to-vesicle transition (MVT) is of great importance from both theoretical and practical points of view. Herein, we studied the effect of compressed CO(2) on the aggregation behavior of dodecyltrimethylammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) mixed surfactants in aqueous solution by means of direct observation, turbidity and conductivity measurements, steady-state fluorescence, time-resolved fluorescence quenching (TRFQ), fluorescence quantum yield, and template methods. Interestingly, all these approaches showed that compressed CO(2) could induce the MVT in the surfactant system, and the vesicles returned to the micelles simply by depressurization; that is, CO(2) can be used to switch the MVT reversibly by controlling pressure. Some other gases, such as methane, ethylene, and ethane, could also induce the MVT of the surfactant solution. A possible mechanism is proposed on the basis of the packing-parameter theory and thermodynamic principles. It is shown that the mechanism of the MVT induced by a nonpolar gas is different from the MVT induced by polar and electrolyte additives.
authors.affiliation: CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Jianling
authors.initials: J
authors.lastname: Zhang
authors.forename: Yueju
authors.initials: Y
authors.lastname: Zhao
authors.forename: Minqiang
authors.initials: M
authors.lastname: Hou
authors.forename: Buxing
authors.initials: B
authors.lastname: Han
authors.forename: Cailan
authors.initials: C
authors.lastname: Yu
authors.forename: Jianping
authors.initials: J
authors.lastname: Ye