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

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.