Compartmentalization and Separation of Aqueous Reagents in the Water Droplets of Water-in-Oil High Internal Phase Emulsions

Abstract

We have compartmentalized aqueous reagents and indicator species within the micrometer-sized water droplets of mixed high internal phase emulsions (HIPEs). Mass transport of the reagents across the micrometer-thickness oil films separating the water droplets followed by reaction with the indicator species produces a visible color change which provides a simple method to measure the trapping times of the reagents. Trapping times have been measured for an uncharged reagent (hydrogen peroxide) and charged reagents (HCl and NaClO) in different HIPEs. The trapping times are discussed in terms of a model in which the transferring species partitions from the water to the oil film followed by a rate-determining step of diffusion across the oil film. Rather surprisingly, it is found that trapping times are of similar orders of magnitude for both uncharged and charged aqueous species transferring across liquid oil films.

Macroporous antibacterial hydrogels with tunable pore structures fabricated by using Pickering high internal phase emulsions as templates

“…HIPEs as unique emulsions with internal phase fractions (IPFs) more than 74 vol% of the total emulsion volume are well known to all of us, and PolyHIPEs are usually synthesized by polymerizing the monomers in the continuous phase of HIPEs and then removing the dispersed phase. [11][12][13][14][15] However, the preparation of C/W HIPEs requires specialized equipment to achieve the required pressures. 7,8 And therefore O/W HIPEs instead of C/W HIPEs were most widely investigated as templates for the fabrication of macroporous hydrogels.…”

Stabilisers for water-in-fluorinated-oil dispersions: Key properties for microfluidic applications

“…However, the partitioning coefficient of most organic molecules in the investigated water-in-oil emulsions is significantly altered when replacing hydrogenated with fluorinated components [51,52]. The hypothesis that interface acts as an effective barrier to the diffusion of molecules was revised by some authors recently [53], suggesting that no significant energy barrier for molecules crossing an interface exists [54]. In this limit, the transport of molecules between emulsion droplets is controlled by the diffusive flux in the continuous phase.…”

“…the continuous phase as the limiting process [54] assuming that no significant energy barrier for molecules crossing the droplet interface exists. Accordingly, they find that the rate limiting step of transport is the diffusion across the continuous phase.…”

The impact of the confinement of reactants on the metal distribution in bimetallic nanoparticles synthesized in reverse micelles

“…It is assumed that k ex is mainly determined by the microemulsion composition [39–42] and the nature of the material is less important. Thus, although the characteristics of the species traversing the channel could modify the intermicellar exchange rate, a single value of k ex was used in this investigation ().…”