Abstract
What measurable physical properties allow one to distinguish surfactant-stabilised from Pickering emulsions? Whereas surfactants influence oil/water interfaces by lowering the oil/water interfacial tension, particles are assumed to have little effect on the interfacial tension. Here we perform interfacial tension (IFT) measurements on three different systems: (1) soybean oil and water with ethyl cellulose nanoparticles (ECNPs), (2) silicone oil and water with the globular protein bovine serum albumin (BSA), and (3) sodium dodecyl sulfate (SDS) solutions and air. The first two systems contain particles, while the third system contains surfactant molecules. We observe a significant decrease in interfacial tension with increasing particle/molecule concentration in all three systems. We analyse the surface tension data using the Gibbs adsorption isotherm and the Langmuir equation of state for the surface, resulting in surprisingly high adsorption densities for the particle-based systems. These seem to behave very much like the surfactant system: the decrease in tension is due to the presence of many particles at the interface, each with an adsorption energy of a few kBT. Dynamic interfacial tension measurements show that the systems are in equilibrium, and that the characteristic time scale for adsorption is much longer for particle-based systems than for surfactants, in line with their size difference. In addition, the particle-based emulsion is shown to be less stable against coalescence than the surfactant-stabilised emulsion. This leaves us with the conclusion that we are not able to make a clear distinction between the surfactant-stabilised and Pickering emulsions.
| Original language | English |
|---|---|
| Pages (from-to) | 1941-1951 |
| Number of pages | 11 |
| Journal | Soft Matter |
| Volume | 19 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - 14 Mar 2023 |
Bibliographical note
Funding Information:We would like to thank prof. Dr Bernard Binks and prof. Dr Adrian Rennie for very helpful discussions. We also would like to thank Dr Jo Janssen from Unilever R & D for helpful suggestions. We would like to thank Paul Kolpakov for his help with the surface tension measurements on SDS solutions. The work of RD is part of the research programme Controlling Multiphase Flow with project number 680-91-012, which is (partly) financed by the Dutch Research Council (NWO) and co-funded by TKI-E&I with the supplementary grant ‘TKI- Toeslag’ for Topconsortia for Knowledge and Innovation (TKI’s) of the Ministry of Economic Af- fairs and Climate Policy. This work took place within the framework of the Institute of Sustainable Process Technology. This work was partially funded by Evodos, Shell.
Publisher Copyright:
© 2023 The Royal Society of Chemistry.
Funding
We would like to thank prof. Dr Bernard Binks and prof. Dr Adrian Rennie for very helpful discussions. We also would like to thank Dr Jo Janssen from Unilever R & D for helpful suggestions. We would like to thank Paul Kolpakov for his help with the surface tension measurements on SDS solutions. The work of RD is part of the research programme Controlling Multiphase Flow with project number 680-91-012, which is (partly) financed by the Dutch Research Council (NWO) and co-funded by TKI-E&I with the supplementary grant ‘TKI- Toeslag’ for Topconsortia for Knowledge and Innovation (TKI’s) of the Ministry of Economic Af- fairs and Climate Policy. This work took place within the framework of the Institute of Sustainable Process Technology. This work was partially funded by Evodos, Shell.
| Funders | Funder number |
|---|---|
| Dutch Research Council (NWO) | 680-91-012 |
| TKI-EI | |
| TKI- Toeslag' for Topconsortia for Knowledge and Innovation (TKI's) of the Ministry of Economic Affairs and Climate Policy | |
| Evodos | |
| Shell |