Destabilising Pickering emulsions by drop flocculation and adhesion

Catherine P Whitby; Hunainah Khairul Anwar; James Hughes

doi:10.1016/j.jcis.2015.11.063

Destabilising Pickering emulsions by drop flocculation and adhesion

J Colloid Interface Sci. 2016 Mar 1:465:158-64. doi: 10.1016/j.jcis.2015.11.063. Epub 2015 Dec 2.

Authors

Catherine P Whitby¹, Hunainah Khairul Anwar², James Hughes²

Affiliations

¹ Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand. Electronic address: C.P.Whitby@massey.ac.nz.
² Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.

PMID: 26674231
DOI: 10.1016/j.jcis.2015.11.063

Abstract

We have investigated how emulsions of water drops coated by organoclay particles destabilise in organic solvents. The drops destabilise and the emulsions undergo a fluid-solid transition if the particles are poorly wetted by the solvent. We show that the drops adhere together and form three-dimensional networks as the fraction of the poor-quality solvent in the mixture increases. Microscopic observations revealed that the drops coalesce into buckled, non-spherical shapes in mixtures rich in poor-quality solvent. A key finding is that destabilisation is favoured under conditions where the energy of adhesion between the particle layers coating drops is comparable to the energy required to detach the particles from the drops. Rupture of the interfacial layer produces particle flocs and uncoated, unstable water drops that settle out of the emulsion.

Keywords: Adhesion; Destabilisation; Flocculation; Particle-stabilised emulsion; Pickering emulsion.