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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Record number 411055
Title Pickering emulsions: Wetting and colloidal stability of hairy particles - A self-consistent field theory
Author(s) Salari, J.W.O.; Leermakers, F.A.M.; Klumperman, B.
Source Langmuir 27 (2011)11. - ISSN 0743-7463 - p. 6574 - 6583.
DOI http://dx.doi.org/10.1021/la104886u
Department(s) Physical Chemistry and Colloid Science
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) oil-water interface - interacting chain molecules - statistical-theory - solid particles - stabilization - adsorption - polymer - phase - microcapsules - surfactants
Abstract The assembly of sterically stabilized colloids at liquid–liquid interfaces is studied with the self-consistent field (SCF) theory using the discretization scheme that was developed by Scheutjens, Fleer, and co-workers. The model is based on a poly(methyl methacrylate) (pMMA) particle with poly(isobutylene) (pIB) grafted to the surface. The stabilizing groups on the particle surface have a significant effect on the interfacial assembly and, therefore, also on the formation and properties of Pickering emulsions. The wetting behavior of the particle is altered by the presence of the stabilizing groups, which affects the equilibrium position of the particles at the interface. The stabilizing groups can also lead to an activation barrier before interfacial adsorption, analogous to the steric repulsion between two particles. These effects are numerically solved with the SCF theory. It is commonly known that flocculating conditions enhance the interfacial adsorption and yield stable Pickering emulsions, which is confirmed in this work. Additionally, it is concluded that those conditions are not an absolute requirement. There is a window of stabilizer concentrations GpIB, 2.2–3.3 mg/m2 pIB, that shows both partial wetting and colloidal stability. The activation barrier for interfacial assembly is 140–550 kBT and is an order of magnitude higher than the colloidal stability. The difference can be attributed to the unfavorable interaction of pIB with water and a difference in geometry (plate–sphere vs sphere–sphere). This study demonstrates the interplay and provides a quantitative comparison between the wetting behavior and the colloidal stability, and it gives a better understanding of the colloidal assembly at soft interfaces and formation of Pickering emulsions in general
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