Water-in-water Pickering Emulsions
Oor, I.S.J. van 't
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Pickering stabilization of dextran/gelatin water-in-water emulsions was investigated using different types of colloidal particles: polystyrene spheres, starch granules, and gibbsite platelets. The polystyrene colloids were synthesized for this research, with particle radii up to 1 µm and zeta-potentials between -40 and +40mV. Surface modi?cations were done to decrease affnity for gelatin, with aluminum chlorohydrate and poly(ethylene glycol). Corn starch granules were prepared using size fractionation, obtaining a particle radius of about 3.5 µm. Rice starch granules of about 2 µm were used as supplied. The gibbsite platelets had a diameter of 167nm ± 18% and a thickness of 6.6nm ± 17 %. The colloidal particles were added to phase separating aqueous dextran/gelatin mixtures. With polystyrene colloids no interfacial adsorption was observed, despite the various modi?cations done to the particles. With both corn and rice starch adsorption was observed, as well as a delay in macroscopic phase separation. However, due to the high buoyant mass of the particles they sedimented, and no stable emulsions were obtained. Gibbsite platelets did provide stabilization, with the highest stabilization observed in systems with an excess of dextran phase, as deduced from analytical centrifugation. Both stable dextran-in-gelatin and gelatin-in-dextran emulsions were observed using confocal microscopy. The exact mechanism of the gibbsite stabilization however remains a subject for further research.