Highly CO_2/N_2?Switchable Zwitterionic Surfactant for Pickering Emulsions at Ambient Temperature

摘要

Cross-linked polymer particles were prepared via surfactant-free emulsion copolymerization of 2-(diethylamino)-ethyl methacrylate (DEAEMA) and sodium methacrylate (SMA) using N,N′-methylenebis(acrylamide) (MBA) as a cross-linker. Generated particles are zwitterionic, possessing unique isoelectric points in the pH range of 7.5-8.0, which is readily tunable through CO_2/N_2 bubbling. The particles were found to be highly responsive to CO_2/N_2 switching, dissolving in water with CO_2 bubbling and precipitating with N_2 bubbling at room temperature. Pickering emulsions of n-dodecane were prepared using these particles as the sole emulsifier. These emulsions can be rapidly demulsified with CO_2 bubbling, resulting in complete oil/water phase separations. Nitrogen bubbling efficiently re-emulsifies the oil with the aid of homogenization. The rapid emulsification/demulsification using CO_2/N_2 bubbling at room temperature provides these cross-linked zwitterionic particles with distinct advantages as functional Pickering surfactants.