Rheology of Pickering emulsions stabilized via cellulosic nanoparticles: yield stress and structural recovery

Pickering emulsions are emulsions stabilized via solid particles in lieu of surfactant molecules. We report utilization of cellulose acetate (CA) nanoparticles prepared by the solvent evaporation process to produce stable oil in water Pickering emulsions probing the effect of CA concentration and the oil/water ratio on the emulsion rheology and stability. Yield stress measurements show that while increase in CA concentrations increases the yield stress, at lower concentrations there is evidence of double yielding. We attempt to explain these trends based on the emulsion droplet size and distribution along with the morphology of the CA NP, correlating the rheology data with microscopic evidence. We postulate that the presence of NP network strands between the droplets at higher CA concentration leads to the sharp distinct microstructure breakdown. While at lower CA concentrations, larger and broader emulsion droplets with insufficient NP linkages show a more discontinuous microstructure breakdown. We further investigate the viability of the synthesized emulsions with two distinct model agricultural cargo including a hydrophobic nematicide, abamectin and a plant growth promoting microbe, Pseudomonas simiae, verifying their performance with a diverse spectrum of tests. Thus, in addition to explaining the fundamental rheology of the CA emulsions, we have demonstrated proof of concept of their potential as a loading platform for agriculture cargos.