Complex Emulsions by Extracting Water from Homogeneous Solutions Comprised of Aqueous Three-Phase Systems

Multiple emulsions
can be obtained by binary and ternary liquid
phase separation. And the use of the aqueous two-phase system provides
a simple route to prepare water-in-water-in-oil (W/W/O) or water-in-water-in-water
(W/W/W) multiple emulsions. It is thus expected that we can fabricate
more complex emulsions by using an aqueous three-phase system. Herein,
we present a simple and versatile method to generate complex emulsions
based on phase separation in homogeneous droplets made up of aqueous
three-phase system: poly­(ethylene glycol) (PEG), poly­(vinyl alcohol)
(PVA) and dextran (DEX) through extracting water from droplets. We
examine the formation process and the effect of mass ratio of each
two components in the three phase system. Emulsion droplets with five
types of morphologies, i.e., binary-core/shell, core/shell-single
phase Janus, ellipsoid Janus, multicore-in-matrix and single core-double
shell morphologies can be formed, depending on the mass ratio of each
two components and modification of PEG with Fe3O4 nanoparticles. We observe transition of core/shell-single phase
Janus to binary-core/shell and single core-double shell to core/shell-single
phase Janus geometry with prolongation of extracting time, and obtain
the geometry map for the formation of different shaped droplets. Due
to different affinities of PEG, PVA and DEX to certain materials,
we functionalize each compartment in the complex emulsion droplets,
and apply the resulting droplet for glucose sensing and the construction
of antibody-mediated targeting drug delivery. This emulsion generation
method is simple and the choice for the component of the aqueous three-phase
system is broad, which can be further extended to generate complex
emulsions from aqueous multiphase systems.