Alkyl Acetamidine Surfactant-Based Microemulsion and Its CO2-Responsive Reversible Switching Properties

CO 2 -responsive switchable microemulsions have attracted significant attention due to their substantial potential in organic synthesis, drug delivery, and nanomaterial preparation. This study presents a microemulsion system composed of N ′-dodecyl- N , N -dimethyl acetamidine, 1-hexanol, brine, and tetradecane. The phase behavior of the microemulsion system was systematically investigated through a salinity scan to access its salinity dependence, while the solubilization ratios were also evaluated. Furthermore, the microstructural characteristics of the microemulsion system were examined using dynamic light scattering, small-angle X-ray scattering, and interfacial tension measurements. A transition from Winsor I to Winsor III, and subsequently to Winsor II, was observed in the alkyl acetamidine surfactant-based microemulsion as salinity increased, with the smallest domain size and most ordered microstructure occurring near the optimal salinity. Notably, the three-phase microemulsion system demonstrated the ability to reversibly switch between emulsification and demulsification upon CO 2 or N 2 injection, showcasing its dynamic responsiveness. This study enhances the understanding of CO 2 -responsive microemulsions and offers potential pathways for sustainable chemical processes. Graphical