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Particles at Fluid Interfaces

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Front. Chem. | doi: 10.3389/fchem.2018.00132

Mixing time, inversion and multiple emulsion formation in a limonene and water Pickering emulsion

  • 1School of Physics and Astronomy, University of Edinburgh, United Kingdom
  • 2School of Chemical and Process Engineering, University of Leeds, United Kingdom

It has previously been demonstrated that particle-stabilized emulsions comprised of limonene, water and fumed silica particles exhibit complex emulsification behavior as a function of composition and the duration of the emulsification step. Most notably the system can invert from being oil-continuous to being water-continuous under prolonged mixing. Here we investigate this phenomenon experimentally for the regime where water is the majority liquid. We prepare samples using a range of different emulsification times and we examine the final properties in bulk and via confocal microscopy. We use the images to quantitatively track the sizes of droplets and clusters of particles. We find that a dense emulsion of water droplets forms initially which is transformed, in time, into a water-in-oil-in-water multiple emulsion with concomitant changes in droplet and cluster sizes. In parallel we carry out rheological studies of water-in-limonene emulsions using different concentrations of fumed silica particles. We unite our observations to propose a mechanism for inversion based on the changes in flow properties and the availability of particles during emulsification.

Keywords: Droplet, interface, emulsification, colloid, Cluster

Received: 16 Feb 2018; Accepted: 09 Apr 2018.

Edited by:

Erica Wanless, University of Newcastle, Australia

Reviewed by:

Cathy E. McNamee, Shinshu University, Japan
To Ngai, The Chinese University of Hong Kong, China  

Copyright: © 2018 Sawiak, Bailes, Harbottle and Clegg. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Paul Clegg, University of Edinburgh, School of Physics and Astronomy, Edinburgh, EH9 3FD, Scotland, United Kingdom, paul.clegg@ed.ac.uk