Destabilization mechanisms in a triple emulsion with Janus drops.

The destabilization mechanism was investigated of a triple Janus emulsion. The inner part of the emulsion consisted of Janus drops of a vegetable oil (VO) and a silicone oil (SO) in an aqueous (W) drop, (VO+SO)/W. This drop, in turn was dispersed in a VO drop forming a double emulsion (VO+SO)/W/VO. Finally, these complex drops generated a complex Janus (SO+VO)/W/VO/SO triple emulsion by being dispersed in a continuous SO phase. The observations were limited to the time dependence of the over-all creaming/sedimentation processes, to the separation of layers of the compounds and to optical microscopy of the drop configuration with time. In the destabilization process the rise of the complex drops, (SO+VO)/W/VO, caused crowding in the upper part of the emulsion, which in turn led to enhanced coalescence, inversion and separation of a dilute vegetable oil emulsion. As a consequence of the separation of VO in the process, the remaining drops contained a greater W fraction and greater density. This change, in turn, resulted in sedimentation of the complex drops to form several high internal ratio morphologies in an SO continuous emulsion in the lower part of the test tube, among them a W/VO/SO emulsion. Finally, an inversion took place into an SO/VO/W double emulsion forming a separate bottom layer.

One-step inversion process to a Janus emulsion with two mutually insoluble oils.

High internal phase ratio (HIPR) aqueous Janus emulsions of two immiscible oils, silicone oil (SO) and a vegetable oil (VO), were prepared using a vibration mixer. The simple HIPR Janus emulsions, (VO + SO)/W, were found at weight fractions of the aqueous phase in excess of 0.3, while at a corresponding fraction of 0.1, a triple emulsion was obtained with the Janus emulsion forming a drop inside the vegetable oil to give a double Janus emulsion, (VO + SO)/W/VO, which in turn formed drops in the silicone oil resulting in a triple Janus emulsion (VO + SO)/W/VO/SO. Increasing the aqueous-phase fraction from 0.1 to 0.3 consequently meant an inversion, of which one intermediate stage was observed: a more complex configuration, e.g., one in which large SO drops with highly distorted VO drops attached were dispersed in a regular aqueous emulsion with spherical Janus (VO + SO) drops. A preliminary investigation was made into the destabilization process of the triple emulsions.

A one-step process to a Janus emulsion.

Aqueous high internal phase volume ratio (O/W 90/10) Janus emulsions of a vegetable oil and a silicone fluid were prepared in a single step emulsification by the common vibrator equipment. The basis for the unique structure is discussed in relation to pair-wise interactions between the components with especial emphasis on the surfactant concentration in the aqueous phase.