Particle Self-Assembly In Ionic Liquid Based Pickering Emulsions

We report the self-assembly of microparticles in ionic liquid based Pickering emulsions, with emphases on the interfacial self-assembled particle structure and the partition preference of free particles in the dispersed and continuous phases.  In ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate)-in-water Pickering emulsions, the polystyrene microparticles form monolayers at ionic liquid-water interfaces and are close-packed either on fully covered emulsion droplets or aggregated on partially covered droplets. Other than equilibrating at the ionic liquid-water interfaces, the microparticles also exhibit partition preference in the dispersed and continuous phases and intriguingly, can even be transported across the ionic liquid-water interfaces.  In oil (polydimethylsiloxane)-in-ionic liquid Pickering emulsions, a unique and new phenomenon is observed: the microparticles can form bridges between the oil droplets, preventing their coalescence but the particles avoid contact with the ionic liquid phase.   Bridging is most prevalent with negatively charged particles, whereas the positively charged particles do not bridge well.