Abstract
Complex emulsions are used to fabricate new morphologies of multiple Janus droplets, evolving from non-engulfing to complete engulfing core/shell configuration. The produced droplets contain an aqueous phase of dextran (DEX) solution and an oil phase, which is mixed with ethoxylated trimethylolpropane triacrylate (ETPTA) and poly(ethylene glycol) diacrylate (PEGDA). The PEGDA in the oil phase is transferred into the aqueous phase to form complex morphologies due to the phase separation of PEGDA and DEX. The effects are investigated including the ratio of oil to aqueous phase, the content of initial PEGDA, DEX and surfactants, and the type of surfactants. DEX/PEGDA-ETPTA core/shell-single phase Janus droplets are formed with an increasing engulfed oil droplet into the aqueous droplet while the ratio of oil to aqueous phase increases or the initial PEGDA content increases. The high DEX content leads to the DEX-PEGDA-ETPTA doublet Janus. The use of surfactants polyglycerol polyricinoleate (PGPR) and Span 80 results in the formation of DEX/PEGDA/ETPTA single core/double shell and DEX/PEGDA-ETPTA core/shell-single phase Janus droplets, respectively. These complex emulsions are utilized to fabricate solid particles of complex shapes. This method contributes to new material design underpinned by mass transfer and phase separation, which can be extended to other complex emulsion systems.
Highlights
New techniques of microfluidic methods[15,16] and phase separation methods[17] have been introduced
A mixed solution of 50 wt% ethoxylated trimethylolpropane triacrylate (ETPTA) and 50 wt% poly(ethylene glycol) diacrylate (PEGDA) was used as the oil phase, 10 wt% DEX solution as the aqueous phase, and liquid paraffin as the continuous phase
A new preparation of complex emulsions is reported based on internal mass transfer of droplet and phase separation of aqueous two-phase system (ATPS)
Summary
New techniques of microfluidic methods[15,16] and phase separation methods[17] have been introduced. The ATPS can be used to prepare multiple emulsions,[28] microcapsules[29] or particles.[30] These new methods are useful in the preparation of complex emulsions, but still subject to some limitations. We combine a microfluidic method with a masstransfer induced phase separation for preparing complex emulsions. The droplets were prepared by using a simple coaxial theta glass capillary device, in which a mixture of ETPTA and PEGDA was the oil phase with a dextran (DEX) solution as the aqueous phase. When the PEGDA in the aqueous droplet reached a certain concentration, PEGDA and DEX were separated into two phases. The change of the droplet morphology was achieved by adjusting the flow ratio of the oil phase to the aqueous phase, the initial content of PEGDA, DEX and surfactants, and the type of surfactants. Once the complex emulsions of various morphologies were obtained, the emulsion droplets could be treated by ultraviolet irradiation to obtain complex particles of various shapes
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