Pluronic F-127-Modified Silica Nanoparticles Stabilize Pickering Emulsions in Eucalyptol–Water Mixtures

Abstract

Silica nanoparticles treated with the hydrophilic triblock copolymer Pluronic F-127 were used to stabilize Pickering emulsions in water/eucalyptol mixtures. The particle–polymer dispersions were employed without removal of unadsorbed polymer, so the systems may be co-stabilized by polymer-associated nanoparticles and residual free Pluronic F-127. Emulsion type depended primarily on the oil volume fraction, ϕe: increasing ϕe induced catastrophic phase inversion from oil-in-water to water-in-oil emulsions, whereas variations in Pluronic F-127 concentration had only a modest effect on emulsion type or stability. Emulsion stability, quantified by a destabilization index, increased as the phase inversion region was approached, indicating that formulations near the inversion boundary are the most resistant to gravitational separation. Droplet-size analysis showed approximately constant mean diameters over the investigated ϕe: range, suggesting that the stability trends are not driven primarily by changes in droplet size. A simple mass-balance estimate indicates that free Pluronic F-127 micelles or aggregates may remain in the continuous phase; however, their possible contribution to the observed stability trends cannot be separated from interfacial and droplet-packing effects using the present data. These findings demonstrate that Pluronic F-127-modified silica dispersions provide a simple route to tune emulsion type and stability in an environmentally friendly oil–water system and support their potential use as carriers for essential-oil-based formulations.