Related Experiment Video
Updated: Jun 2, 2026
10:20
In vitro Digestion of Emulsions in a Single Droplet via Multi Subphase Exchange of Simulated Gastrointestinal Fluids
Published on: November 18, 2022
High internal phase emulsions under shear. Co-surfactancy and shear stability
Peter N Yaron1, Andrew J Scott, Philip A Reynolds
1Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia.
The Journal of Physical Chemistry. B
|April 20, 2011
Summary
Adding small amounts of polyamide-based cosurfactants (PAM) significantly alters the rheology of high-internal phase aqueous-in-oil emulsions (HIPEs). These PAMs lower interfacial tension, leading to droplet deformation and reduced yield stress under shear.
Area of Science:
- Colloid and Surface Science
- Rheology
- Materials Science
Background:
- High-internal phase aqueous-in-oil emulsions (HIPEs) are complex fluids with applications in various industries.
- The rheological properties of HIPEs are strongly influenced by surfactant choice and concentration.
- Understanding the relationship between emulsion structure and rheology is crucial for controlling their performance.
Purpose of the Study:
- To investigate the impact of water-soluble polyamide-based cosurfactants (PAM) on the rheology of polyisobutylene-based surfactant (PIBSA) stabilized HIPEs.
- To elucidate the structural origins of rheological changes using simultaneous in situ rheology and small-angle neutron scattering (SANS).
- To understand the role of PAM in altering interfacial properties and droplet behavior under shear.
Main Methods:
- Rheological measurements of HIPEs with and without PAM under shear.
- Simultaneous in situ small-angle neutron scattering (SANS) to probe emulsion structure.
- Interfacial tension measurements.
- Analysis of surfactant displacement and micelle formation.
Main Results:
- PAM drastically lowers the droplet-oil interfacial tension by displacing PIBSA.
- This displacement leads to significant droplet deformation under shear and a much-lowered emulsion yield stress.
- PAM alters the responsiveness of the surfactant monolayer to shear-induced shape changes.
- PAM influences PIBSA micelle size and content in the oil phase.
- High shear rate viscosities, shear thinning, and thickening remain largely unaffected by PAM.
Conclusions:
- The addition of PAM fundamentally alters HIPE rheology by modifying interfacial properties and droplet behavior under shear.
- Droplet size, flattening, and linkage are key determinants of viscosity, more so than interfacial tension at high shear rates.
- Droplet motion under shear likely involves sliding past each other with minimal transient deformation.
Related Concept Videos
01:27Surface Active Agents
Surfactants, named for their behavior at interfaces, positively adsorb at the interfaces of two phases, reducing interfacial tension. Their versatility as emulsifiers, detergents, and foaming agents stems from this ability. Surfactants, often termed amphiphiles, share the property of amphipathy, with molecules having both hydrophilic and hydrophobic portions. The hydrophilic part is called the head, and the hydrophobic part, including an elongated alkyl substituent, forms the tail.Surfactants...
01:30Micelles
Micelle formation is an intricate process that hinges on the properties of amphiphilic or amphipathic molecules and the conditions of the system in which they are found. Amphiphilic molecules, which have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, play a critical role in this process.In aqueous environments, these molecules arrange themselves such that their hydrophilic heads are turned towards the water phase, while their hydrophobic tails are oriented away...
03:22Colloids
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
01:29The Colloidal State
The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called the...
01:09Colloidal precipitates
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
01:17Colloids and Suspensions
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...