Bicontinuous Biphasic Liquid Emulsions from Ternary Fluid Mixtures

Bicontinuous interfacially jammed emulsion gels (bijels) are a unique class of soft matter that is produced by arresting spinodal decomposition of biphasic mixtures via interfacial attachment and jamming of particles. Several strategies to form bijels including thermal quenching of homogenous binary mixtures and shearing phase-separated biphasic mixtures in the presence of neutrally wetting particles have been introduced. As a complementary method, we explore the formation of bijels from a homogenous ternary mixture of water, oil and co-solvent. Phase separation is triggered by inducing the removal of the co-solvent via extraction or evaporation. The use of silica nanoparticles and ionic surfactants enables continuous and scalable manufacturing bijels with controllable morphologies and domain sizes down to a few hundreds of nanometers. This presentation will describe the effect of solvent removal process (extraction vs. vaporization) on the morphology and microscale structure of bijels.  Surfactant-free bijels stabilized by mixtures of hydrophobic and hydrophilic nanoparticles can be produced; the ratio of these two particles must be changed depending on the polarity of the oil phase, enabling the fabrication of bijels with a wide range of oils of varying polarity. Moreover, we demonstrate that bicontinuous emulsion gels can be produced by inducing partial coalescence of nanoparticle-covered emulsion droplets via nucleation and growth, resulting in bijels with unique microstructures that are substantially different from those observed in spinodal decomposition-based bijels.