Experiment and simulation studies on the mesostructures of gemini (12-3-12,2Br−)–SDS–H2O ternary

Abstract

Gemini is defined as a surfactant made up of two identical amphiphilic moieties connected by a spacer group at the level of head groups or the alkyl chains close to the head groups. Mesostructures or morphologies of mixed surfactant solutions containing cationic gemini (12-3-12,2Br−) and anionic SDS have been studied by both experiments and simulations.Negative-staining transmission electron microscope was used to determine the structures in different regions of the ternary, most of those regions are occupied by multilamellar phases in which vesicles coexist with micelles when the solutions are dilute. At higher surfactant concentrations, the lamellar phase, rodlike micelle phase, as well as other unique structures such as cylindrical micelles formed by short rodlike ones are observed.For simulations, we adopted dissipative particle dynamics (DPD) technique. With carefully chosen parameters, especially the conservative term, we could reproduce a great variety of mesostructures including spherical micelles, rodlike micelles, planar micelles, network with junctions, bilayer membranes as well as multilamellar aggregates, most of which can be found in corresponding experimental work. DPD results also reveal vividly the self-assembling mechanism that the dispersed surfactant molecules are organized to form small micelles, then fused and twisted to encapsulate water to form vesicles.