Pickering high internal phase emulsion costabilized by a low amount of bio-based rigid surfactant with microsilica via depletion interaction and synergistic effect

A series of green bio-based polyether surfactant were synthesized based on dehydroabietic acid and used to construct Pickering high internal phase emulsions (HIPEs) with microsilica particles which the dispersed phase fraction could up to 90%. Such surfactants have a high surface activity so that the Pickering HIPEs could be stabilized stably at low concentrations with micron-size silica. The microstructure, droplet size and rheology property of Pickering HIPEs could be regulated by varying the microsilica content or dispersed phase fraction. The QCM-D measurements revealed that the nonionic surfactant could adsorb on surface of silica particles, giving rise to the change of wettability of the hydrophilic particles and rendering the particles surface-active. The coated particles were more likely to adsorb at the oil-water interface of droplets. The synergistic effects of hydrophilic silica particles and this nonionic surfactant promoted the formation of stable Pickering HIPEs. Moreover, the depletion interaction between droplets and hydrophilic particles was also the vital factor in the stability of the Pickering HIPEs. Once particles were adsorbed, particles at the interface were inhibited desorption by depletion attraction. This work suggests another possible mechanism for better stability of Pickering HIPEs in nonionic surfactant/particles system, and our strategy to preparing Pickering HIPEs is environmentally friendly by using a bio-based surfactant, which has wide potential application in cosmetics, pharmaceuticals, food, environmental protection, materials, and so on.