Emulsions stabilised solely by colloidal particles

Aveyard, Robert; Binks, Bernard P.; Clint, John H.

doi:10.1016/s0001-8686(02)00069-6

Cited by 2,200 publications

(1,929 citation statements)

References 62 publications

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“…The packing parameter of the surfactant at the oil/water interface is determined by how hydrated the polar head groups are by water and how solvated the hydrophobic tails are by the oil phase. 63 For hydrophilic surfactants, the polar head group tends to take up more room than the chain and the monolayers curve around the oil to give an o/w emulsion. The opposite is true for hydrophobic surfactants, with the area of their lipophilic chain taking up more space than the head group, hence giving w/o emulsions.…”

Section: Pickering Emulsionsmentioning

confidence: 99%

“…The opposite is true for hydrophobic surfactants, with the area of their lipophilic chain taking up more space than the head group, hence giving w/o emulsions. 63 In contrast to conventional surfactants colloidal particles that adsorb to the oil or air/water interface are not amphiphilic but are nevertheless surface-active. For solid particles sitting at an oil-water interface, it is the particle wettability that dictates the emulsion type.…”

Section: Pickering Emulsionsmentioning

confidence: 99%

“…In this case only weak, reversible adsorption is anticipated at the oil-water interface. [63][64] This high energy of particle attachment makes Pickering emulsions far more stable than surfactants, with the adsorbed particles providing a strong steric barrier to droplet coalescence. Colloidal particles such as silica sols [66][67] and polystyrene latexes 68 have been shown to be effective Pickering emulsifiers.…”

Section: Pickering Emulsionsmentioning

confidence: 99%

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Covalently Cross-Linked Colloidosomes

et al. 2010

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Model poly(glycerol monomethacrylate)-based macromonomers have been used to prepare sterically stabilized polystyrene latexes by either aqueous emulsion or alcoholic dispersion polymerization, affording mean latex diameters of approximately 107 or 1188 nm respectively as judged by dynamic light scattering. Such PGMA50−PS latexes have appropriate surface wettability to stabilize 25−250 μm oil-in-water Pickering emulsions, depending on the latex concentration and oil type. Colloidosomes were formed by covalent cross-linking of the hydroxyl-functional stabilizer chains from within the oil droplets using a polymeric diisocyanate (tolylene 2,4-diisocyanate-terminated poly(propylene glycol) [PPG-TDI]. This oil-soluble cross-linker was confined within the oil droplets, allowing colloidosomes to be prepared at 50 vol % solids without any aggregation. The resulting microcapsules survive removal of the internal oil phase using excess alcohol, unlike the noncross-linked Pickering emulsion precursor. These observations confirm the robust nature of these covalently stabilized colloidosomes. A method for controlling the permeability of these colloidosomes by exploiting the solvent properties of binary oil mixtures has also been evaluated. Finally, microcapsule permeability has been explored via dye release experiments. Less permeable microcapsules can be obtained by deposition of polypyrrole onto the colloidosome exterior.

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Section: Pickering Emulsionsmentioning

confidence: 99%

Section: Pickering Emulsionsmentioning

confidence: 99%

Section: Pickering Emulsionsmentioning

confidence: 99%

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Covalently Cross-Linked Colloidosomes

et al. 2010

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“…The spontaneous assembly of nanoparticles to form adsorbed monolayers at fluid-fluid interfaces has been exploited for stabilization of emulsions and foams [1][2][3][4][5] , for creating capsules and nanoporous membranes [6][7][8] , and has found application in phase-transfer catalysis 9,10 and enhanced oil recovery 11 .…”

Section: Introductionmentioning

confidence: 99%

Forced Desorption of Nanoparticles from an Oil–Water Interface

2011

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While nanoparticle adsorption to fluid interfaces has been studied from a fundamental standpoint and exploited in application, the reverse process, i.e. desorption and disassembly, remains relatively unexplored. Here we demonstrate the forced desorption of gold nanoparticles capped with amphiphilic ligands from an oil-water interface. A monolayer of nanoparticles is allowed to spontaneously form by adsorption from an aqueous suspension onto a drop of oil, and is subsequently compressed by decreasing the drop volume. The surface pressure is monitored by pendant drop tensiometry throughout the process. Upon compression, the nanoparticles are mechanically forced out of the interface into the aqueous phase. An optical method is developed to measure the nanoparticle area density in situ. We show that desorption occurs at a coverage that corresponds to close packing of the ligand-capped particles, suggesting that ligand-induced repulsion plays a crucial role in this process. * kstebe@seas.upenn.edu 2

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“…4,5 Notably, apart from the system we focus on in this Article, all other Pickering emulsions are only of kinetic and not thermodynamic stability. 6 To make the distinction between common, metastable Pickering emulsions and the special type of thermodynamically stable Pickering emulsions investigated here, the thermodynamically stable emulsions are also sometimes termed solid-stabilized equilibrium emulsions. 3 In contrast to other oil-water systems which require significant energy input for their formation, for example, by mechanical mixing, thermodynamically stable emulsions form spontaneously upon mixing of the components.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Equilibrium Pickering Emulsions—A Matter of Time Scales

Kraft¹,

Luigjes²,

Folter³

et al. 2010

J. Phys. Chem. B

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A new class of equilibrium solid-stabilized oil-in-water emulsions harbors a competition of two processes on disparate time scales that affect the equilibrium droplet size in opposing ways. The aim of this work is to elucidate the molecular origins of these two time scales and demonstrate their effects on the evolution of the emulsion droplet size. First, spontaneous emulsification into particle-covered droplets occurs through in situ generation of surface-active molecules by hydrolysis of molecules of the oil phase. We show that surface tensions of the oil-water interfaces in the absence of stabilizing colloidal particles are connected to the concentration of these surface-active molecules, and hence also to the equilibrium droplet size in the presence of colloids. As a consequence, the hydrolysis process sets the time scale of formation of these solid-stabilized emulsions. A second time scale is governing the ultimate fate of the solid-stabilized equilibrium emulsions: by condensation of the in situ generated amphiphilic molecules onto the colloidal particles, their wetting properties change, leading to a gradual transfer from the aqueous to the oil phase via growth of the emulsion droplets. This migration is observed macroscopically by a color change of the water and oil phases, as well as by electron microscopy after polymerization of the oil phase in a phase separated sample. Surprisingly, the relative oil volume sets the time scale of particle transfer. Phase separation into an aqueous phase and an oil phase containing colloidal particles is influenced by sedimentation of the emulsion droplets. The two processes of formation of surface-active molecules through hydrolysis and condensation thereof on the colloidal surface have an opposite influence on the droplet size. By their interplay, a dynamic equilibrium is created where the droplet size always adjusts to the thermodynamically stable state.

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Emulsions stabilised solely by colloidal particles

Cited by 2,200 publications

References 62 publications

Covalently Cross-Linked Colloidosomes

Covalently Cross-Linked Colloidosomes

Forced Desorption of Nanoparticles from an Oil–Water Interface

Evolution of Equilibrium Pickering Emulsions—A Matter of Time Scales

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