Pickering Emulsions\nStabilized with Millimeter-Sized\nPolymer Plates

Hexagonal polymer plates of (sub)millimeter size that\nwere uniform\nin shape and size were used as a stabilizer for emulsions, and the\ncorrelations of plate size, oil polarity, and plate dispersing media\nbefore emulsification with the formability, type, and droplet shape\nof emulsions were studied. The formability of the emulsions was improved\nby decreasing the plate size. The lower the oil polarity was, the\nmore preferably O/W-type emulsions were formed, and as the oil polarity\nincreased, the formability of W/O-type emulsions increased, whereas\ntoo high of an oil polarity resulted in no emulsion formation or macrophase\nseparation of the oil dispersion of the plates and water. Furthermore,\nwhen the plate dispersing medium before emulsification was oil, the\nplates tended to be lipophilic compared with those dispersed in water\nbefore emulsification. In addition, we confirmed that there was a\ncorrelation between the droplet/stabilizer size ratio and droplet\nshape: when the droplet/plate size ratios are >2, droplets with\nnear-spherical\nshapes are formed; when the size ratios are between 1 and 2, droplets\nwith polyhedral shapes (e.g., hexahedral and tetrahedral shapes) are\nformed; and when the size ratios are <1, sandwich-shaped droplets\nare formed. Droplets with similar structures tended to form if the\ndroplet/plate size ratios were close, even though the sizes of the\nplate and droplet were different.