Demulsification of (W1 +W2 +W3)/O reverse Cerberus emulsion from vibrational emulsification

Abstract

(W1 +W2 +W3)/O reverse Cerberus emulsion, possessing aqueous environments with separated domains and sharp boundary and especially potential application in biomimetic compartmentalization, is newly emerged aqueous-based multiple emulsion. Thus, the demulsification and stability of reverse Cerberus emulsion, are of vital importance. However, the demulsification process of Cerberus droplet is complicated due to multiple interfaces, anisotropic nature, and the random orientation. Herein, demulsification pattern and stability of reverse Cerberus emulsion are demonstrated by Turbiscan and microscopy. Coalescence and sedimentation are found to dominate the demulsification process. During the coalescence process, two Cerberus droplets coalesce to form a temporary intermediate droplet with a multi-phase morphology, which slowly evolves into a larger Cerberus droplet. Then larger aqueous droplets sediment to form eventually separated multiple aqueous layers. Both surfactant FC-4430 and polymer PEG8000(aq) contribute cooperatively to the stability of emulsion. A critical PEG8000(aq)/FC-4430 mass ratio is found at a fixed Na2CO3(aq) content, at which the emulsion has the fastest demulsification speed. The dominant factor stabilizing emulsion shifts from FC-4430 to PEG8000 beyond this mass ratio. All of these will have implications for future applications of aqueous based multiple emulsions in fields of biotechnology, artificial cell and pharmacology.