Spontaneous Vesicle Formation of Mixtures of Double-Chain Cationic Surfactants with a Different Counterion

Abstract

Aggregate formation of a didodecyldimethylammonium bromide (DDAB) and didodecyldimethylammonium chloride (DDAC) mixture in aqueous solution was investigated. The concentration vs composition diagram of aggregate formation was constructed by analyzing the surface tension, turbidity, and electrical conductivity data. The cryogenic transmission electron microscopy was applied to several representative points in the diagram and provided information of the morphology of aggregates. The sequence of monomer (m) - m + small aggregate (A) - m + A + vesicle (V) - m + V was concluded with increasing total concentration of surfactants at all mixing ratios. The compositions of counterions in A and V were estimated on the basis of thermodynamic consideration and examined from the viewpoint of asymmetry of constituents and uneven distribution between outer and inner monolayers of a vesicle bilayer. Vesicle surfaces were suggested to abound in chloride ions compared to bulk solution, which is opposite to spherical micelle surfaces.

Aggregation and pH Responsive Behavior of Thioester Surfactants and Formation of Disulfide Linkages in Aqueous Solutions

“…The thioester group of the surfactant in the inner layer of the vesicles could protrude toward the outer layer. The vesicles formed from C 12 12SAc had an interdigitated structure that alleviated the electrostatic repulsion between the headgroups as The vesicle formation in the case of DDAB has been verified by cryogenic transmission electron microscopy studies 9,10 . The cvc of DDAB can be determined conveniently by the light scattering method 13 .…”

“…Therefore, control of surfactant aggregation will lead to controlled release of the solubilized substances in the micelles. Didodecyldimethylammonium bromide DDAB is a wellknown surfactant that aggregates into vesicles 9,10 .…”

Aggregation Behavior of Disulfide Linked Gemini Surfactants Compared to that of Double Tailed Surfactants

“…The vesicle formation of DDAB was already indicated by the cryogenic transmission electron microscopy 3,4 . Supposing DDAB will form vesicles at a certain concentration, we checked the cvc of DDAB by convenient light scattering method.…”

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

“…The vesicle formation of DDAC has been investigated previously by the cryogenic transmission electron microscopy cryo-TEM 5 . The CVC of DDAC was verified using the pyrene fluorescence probe method, to determine if DDAC forms vesicles at a certain concentration.…”

“…Stimuli such as redox, light, and pH have been used to trigger release 1 4 . Since doubletailed surfactants such as didodecyldimethylammonium chloride DDAC are known to form vesicles 5 , hydrophilic solubilizates can be encapsulated inside the aqueous core of the vesicle. However, DDAC has no cleavable or responsive groups in the amphiphilic structure.…”