Destabilization of a dual emulsion to form a Janus emulsion

A vegetable oil (VO) was added to an emulsion of silicone oil in water (SO/W) with mixing limited to once turning the test tube upside down. Initially, the VO was dispersed into virtually centimeter-sized drops and the emulsion contained effectively no Janus drops, while after 1 h of agitation at a...

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Bibliographic Details
Published in:Colloid and polymer science 2014-09, Vol.292 (9), p.2319-2324
Main Authors: Hasinovic, H., Friberg, S. E., Kovach, I., Koetz, J.
Format: Article
Language:English
Subjects:
Applied sciences
Characterization and Evaluation of Materials
Chemistry
Chemistry and Materials Science
Colloidal state and disperse state
Complex Fluids and Microfluidics
Emulsions. Microemulsions. Foams
Exact sciences and technology
Food Science
General and physical chemistry
Inorganic and organomineral polymers
Nanotechnology and Microengineering
Original Contribution
Physical Chemistry
Physicochemistry of polymers
Polymer Sciences
Properties and characterization
Soft and Granular Matter
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Description
Summary:A vegetable oil (VO) was added to an emulsion of silicone oil in water (SO/W) with mixing limited to once turning the test tube upside down. Initially, the VO was dispersed into virtually centimeter-sized drops and the emulsion contained effectively no Janus drops, while after 1 h of agitation at a low level to prevent creaming, drops of 50–100-μm size of the two oils were observed: in addition to an insignificant number of Janus drops. The topology of the latter showed them to emanate from flocculated individual drops of the two oils, but with no discernible effect by the interfacial tension equilibrium on the drop topology. Continued gentle mixing gave increasing fraction of Janus drops of increased size with a topology gradually approaching the one expected from the interfacial equilibrium at the contact line. The spontaneous formation of Janus drops indicated a reduction of the interfacial free energy in the process and the interfacial energy difference between separate and Janus drops was calculated for an appropriate range of interfacial tensions and for all oil fractions. The calculations enabled a distinction of the decrease due to interfacial area changes from the reduction of interfacial tensions per se, with the latter only a minor fraction. Figure ᅟ
ISSN:0303-402X
1435-1536
DOI:10.1007/s00396-014-3263-3