Understanding droplet bridging in ionic liquid-based Pickering emulsions

Frost, Denzil S.; Schoepf, Jared; Nofen, Elizabeth; Dai, Lenore L.

doi:10.1016/j.jcis.2012.06.010

Cited by 26 publications

(20 citation statements)

References 48 publications

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“…Several examples of such a conguration have already been reported in the literature, either with isolated emulsion lms where two colloid-laden interfaces are brought into contact in a controlled manner [43][44][45] or with emulsions. 41,[46][47][48] In particular, bridging monolayer formation has been strongly hypothesised and demonstrated for emulsions containing drops sparsely protected by charged particles (with a surface coverage as low as 5%) and seems to be at the origin of the astonishing kinetic stability of the emulsions due to spontaneous particle accumulation in the contact zone between drops forming a locally dense particle layer that provides steric hindrance against drop coalescence. 37,38,43,49 Bridging not only occurs with rigid particles but also with so particles that are able to deform and span two interfaces as reported recently in a study on temperaturesensitive poly(NIPAM)-based microgels.…”

Section: Resultsmentioning

confidence: 99%

Emulsions stabilised by whey protein microgel particles: towards food-grade Pickering emulsions

et al. 2014

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We have investigated a new class of food-grade particles, whey protein microgels, as stabilisers of triglyceride-water emulsions. The sub-micron particles stabilized oil-in-water emulsions at all pH with and without salt. All emulsions creamed but exhibited exceptional resistance to coalescence. Clear correlations exist between the properties of the microgels in aqueous dispersion and the resulting emulsion characteristics. For conditions in which the particles were uncharged, fluid emulsions with relatively large drops were stabilised, whereas emulsions stabilized by charged particles contained smaller flocculated drops. A combination of optical microscopy of the drops and spectrophotometry of the resolved aqueous phase allowed us to estimate the interfacial adsorption densities of the particles using the phenomenon of limited coalescence. We deduce two classes of particle arrangement. Complete adsorption of the particles was obtained when they were neutral or when their charges were screened by salt resulting in at least one particle monolayer at the interface. By contrast, only around 50% of the particles adsorbed when they were charged with emulsion drops being covered by less than half a monolayer. These findings were supported by direct visualization of drop interfaces using cryo-scanning electron microscopy. Uncharged particles were highly aggregated and formed a continuous 2-D network at the interface. Otherwise particles organized as individual aggregates separated by particle-free regions. In this case, we suggest that some particles spread at the interface leading to the formation of a continuous protein membrane. Charged particles displayed the ability to bridge opposing interfaces of neighbouring drops to form dense particle disks protecting drops against coalescence; this is the main reason for the flocculation and stability of emulsions containing sparsely covered drops.

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Section: Resultsmentioning

confidence: 99%

Emulsions stabilised by whey protein microgel particles: towards food-grade Pickering emulsions

et al. 2014

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“…This effect has been observed by Zhang et al using layered double-hydroxide particles for the preparation of Pickering emulsions. Moreover, droplet bridging has been observed by Frost et al when ionic liquids are used for Pickering emulsion preparation.…”

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confidence: 89%

Inverse Pickering Emulsion Stabilized by Exfoliated Hexagonal-Boron Nitride (h-BN)

et al. 2017

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The formation of inverse Pickering emulsions using exfoliated hexagonal boron nitride (h-BN) as an effective particulate stabilizer without using any surfactants is reported for the first time. The stability and the type of h-BN Pickering emulsions formulated with different BN concentrations and by varying oil/water (o/w) ratios are studied and discussed. First the emulsion structure is analyzed microscopically through optical and epifluorescence microscopy and macroscopically by the study of the rheological behavior. The average droplet size decreases with h-BN concentration whereas the emulsions achieve good stability at 2 wt % BN concentrations and for a 1:1 o/w ratio. In all formulations, the emulsions are of water-in-oil (w/o) type due mainly to the hydrophobicity of h-BN.

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“…39 In contrast to those of the water−oil interfaces, the interfacial tensions of ILbased interfaces are very low (about several-20 mN/m). 40 The transportation of particles from water to the IL phase was also observed at the water−IL interface. 41 To date, there have been some reports on IL-containing non-aqueous microemulsions utilizing low molecular weight surfactants, and the most frequently used surfactant is nonionic TX-100.…”

Section: ■ Introductionmentioning

confidence: 97%

“…Room-temperature ionic liquids (IL) exhibit low volatility, chemical stability, high conductivity, excellent solubility, and tunable solvent properties and could be utilized as a “green” water alternative to prepare non-aqueous emulsions . In contrast to those of the water–oil interfaces, the interfacial tensions of IL-based interfaces are very low (about several-20 mN/m) . The transportation of particles from water to the IL phase was also observed at the water–IL interface .…”

Section: Introductionmentioning

confidence: 99%

Amphiphilic Double-Brush Copolymers with a Polyurethane Backbone: A Bespoke Macromolecular Emulsifier for Ionic Liquid-in-Oil Emulsion

Gao

Xiang

et al. 2021

Langmuir

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The study on ionic liquid (IL)-based emulsions is very interesting due to the "green" quality and potential wide applications of ILs, whereas the emulsifiers for the formation of ILbased emulsions are extremely limited and mainly centered on low molecular weight surfactants. In this work, synthesis of amphiphilic double-brush copolymers (DBCs) and their application as bespoke macromolecular emulsifiers for the formation of IL-containing non-aqueous emulsions are described. DBCs consisted of a polyurethane (PU) backbone and poly(N,N-dimethyl acrylamide) (PDMA) and poly(methyl methacrylate) (PMMA) chains that were grafted simultaneously at the same reactive site along the PU backbone (PU-g-PDMA/PMMA), which were synthesized through the combination of polyaddition and the reversible-deactivation radical polymerization reactions. Highly stable [Bmim][PF 6 ]-in-benzene emulsions could be gained by adopting PU-g-PDMA/PMMA DBCs as macromolecular emulsifiers at a low content, such as 0.025 wt %. On the basis of the stability and the size of emulsion droplets, PU-g-PDMA/PMMA DBCs exhibited much better emulsifying performances than their analogues, including PU-g-PDMA, PU-g-PMMA, and PDMA-b-PMMA copolymers. Such excellent emulsifying performances of PU-g-PDMA/PMMA DBCs were due to high interfacial activities. PU-g-PDMA/PMMA DBCs exhibited higher capabilities in lowering the interfacial tension of the [Bmim][PF 6 ]−benzene interface than their analogues. A large energy barrier to desorption of adsorbed PU-g-PDMA/PMMA DBCs from the interface contributed to high stability of the [Bmim][PF 6 ]-in-benzene emulsion.

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Understanding droplet bridging in ionic liquid-based Pickering emulsions

Cited by 26 publications

References 48 publications

Emulsions stabilised by whey protein microgel particles: towards food-grade Pickering emulsions

Emulsions stabilised by whey protein microgel particles: towards food-grade Pickering emulsions

Inverse Pickering Emulsion Stabilized by Exfoliated Hexagonal-Boron Nitride (h-BN)

Amphiphilic Double-Brush Copolymers with a Polyurethane Backbone: A Bespoke Macromolecular Emulsifier for Ionic Liquid-in-Oil Emulsion

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