Temperature-induced micelle transition of gemini surfactant in aqueous solution

The viscosity and morphology of gemini surfactant in aqueous solution at various temperatures are investigated by rheometer and transmission electron microscopy with a freeze fracture replication technique. The viscosity of 18-3-18 or 16-3-16 reaches its maximum when the solution temperature is near the Krafft temperature of the surfactant. The morphology of a gemini surfactant in aqueous solution is strongly influenced by the temperature: vesicles or sphere-like aggregates are formed in the dilute solution of 18-3-18 under 25 °C environment; when the solution temperature goes up to 50 °C, such aggregates will transit to worm-like micelles with the length of each from 100 nm to 400 nm; meanwhile, the increase of concentration may lead to the formation of network; however, the worm-like micelles or network will transit to vesicles or sphere-like aggregates again when the temperature reaches 80 °C.