Mass transfer induced phase separation of ternary mixtures: From onion emulsions to asymmetric bijel structures and the analysis of their mechanical properties

Condensed Matter lunchtime seminar

Mass transfer induced phase separation of ternary mixtures: From onion emulsions to asymmetric bijel structures and the analysis of their mechanical properties

  • Event time: 1:00pm
  • Event date: 3rd September 2015
  • Speaker: Martin Haase (University of Pennsylvania)
  • Location: Room 2511,

Event details

In everyday life, ternary phase separation takes place when one pours the Greek spirituous Ouzo in a glass of water. If not already intoxicated, the observer will notice the scattering of light in the liquid mixture. Tiny oil droplets have nucleated upon dilution of their solvent, ethanol.

In the first part of my talk I will present an analogous phenomena occurring when forming a single droplet composed of a ternary liquid mixture in a continuous phase. We show that for this case, phase separation occurs via self-similar cycles of mass transfer, spinodal decomposition or nucleation, and coalescence, forming multiple layers. Mapping out the phase diagram demonstrates a linear relation between concentric layer diameters, whose slope depends on the initial ternary composition.

The second part of my talk will introduce the formation of bicontinuous interfacially jammed emulsion gels (bijels) by ternary phase separation. Introducing commercially available silica nanoparticles and ionic surfactants to the ternary mixture allows us to perpetually form bijel microparticles, fibers, and membranes. We study the dependence of fiber morphology on different control parameters such as particle and surfactant concentration. Confocal and electron microscopy reveal hierarchical and asymmetric fiber architectures remarkably similar to polymer membranes formed via non-solvent induced phase inversion. Based on a newly developed, in-situ technique, we have measured the yield strengths of the bijel fibers to range from a few hundred Pa to several kPa.

Haase, M. F., Brujic, J., "Tailoring of High?Order Multiple Emulsions by the Liquid?Liquid Phase Separation of Ternary Mixtures." Angewandte Chemie International Edition 53.44 (2014): 11793-11797.

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..

Find out more about Condensed Matter lunchtime seminars.