Rheology and structure of macro- and nano-emulsions with adhesive droplets

In this work, we investigate the viscoelastic and flow properties of oil-in-water nanoemulsions to verify rheological scaling models of macroemulsion systems. Emulsions were prepared using silicone oil with different average droplet sizes (ranging from 1 µm to below 100 nm) dispersed in sodium dodecyl sulfate solution above the critical micelle concentration. Droplet size distributions were narrow and remained unchanged for all the samples. Viscoelastic responses and yielding of emulsions were examined as a function of dispersed phase volume fractions (35 – 65 %) for each of the droplet sizes. The range of volume fractions for the samples was obtained via an evaporation-dilution technique. We elucidate the experimental result using the theoretical models for interdroplet interactions. The scaling of rheological properties with Laplace pressures becomes invalid in the nanoemulsion regime. The liquid, gel, and glass states are investigated based on the elastic modulus, yield stress and yield strain of studied adhesive emulsions.