CO2-responsive Pickering emulsions stabilized by in-situ generated ionic liquids and silica nanoparticles

Abstract Stimuli-responsive Pickering emulsions have attracted increasing interest because of the advantages of applications in numerous industrial processes. In this work, Pickering emulsions have been obtained by using negatively charged silica nanoparticles in association with very small amount of CO 2 -responsive ionic liquids as stabilizer. Ionic liquids N -alkylimidazole bicarbonates ([C n im] + HCO 3 − , n = 6, 8, 10, 12, 14) are in-situ generated by bubbling CO 2 into aqueous solution of N -alkylimidazoles (C n im, n = 6, 8, 10, 12, 14), and this process is reversible by removal of CO 2 with bubbling of N 2 . Thus the Pickering emulsions may be switched multiple times between emulsification and demulsification states by alternatively bubbling and removal of CO 2 at 25 °C. The effect of concentration and alkyl chain length of [C n im] + HCO 3 − on Pickering emulsions is investigated systematically, and the possible mechanism of CO 2 -responsive Pickering emulsion is also studied by conductivity, surface tension, zeta potential, adsorption isotherm, water contact angle and 13 C NMR spectroscopy. This CO 2 -responsive Pickering emulsion is cheap, simple, eco-friendly, and may have potential applications in emulsification and demulsification.