High Internal Phase Pickering Emulsions as Templates for a Cellulosic Functional Porous Material

Emulsions stabilized by solid particles (Pickering emulsions) are remarkably more resistant to coalescence than emulsions generated with molecular surfactants. If enriched to at least 0.74 by volume fraction of the dispersed phase, then these so-called high internal phase Pickering emulsions (HIPPEs) find important use as templates for the fabrication of a wide spectrum of functional porous materials. Starting with ethyl cellulose (EC)—a nontoxic, food-grade, and biocompatible polymer derived from abundant cellulose—we show how spherical EC nanoparticles can be used to generate oil-in-water (O/W) or water-in-oil (W/O) Pickering emulsions without surfactants. We explore the conditions of ionic strength, oil volume fraction, and EC nanoparticle concentration under which HIPPEs with an internal phase volume fraction of 0.76 ± 0.04 are produced. Using EC nanoparticle-stabilized HIPPEs as a template, we then fabricate a hydrophobic/oleophilic polymeric porous material, which selectively absorbs oil, collects an oil spill from the surface of water, and breaks an O/W Pickering emulsion to its constituents.