Rheology of glassy and jammed emulsions*

We study the rheology of monodisperse and polydisperse emulsions with various mean droplet sizes. Above a critical volume fraction φ, these systems exhibit solid-like behavior and possess a yield stress. Previous simulation work suggests that for small thermal particles, rheology will see a glass transition at φ≈0.58; for large athermal systems, rheology will see a jamming transition at φ≈0.63. However, for intermediate sized droplets at the crossover of thermal and athermal regimes, the glass and jamming transitions may both be observable in the same sample. We use a rheometer to shear different sizes of TPM emulsion droplets. By varying the shear rate and particle size, our experiments cover a wide range of Péclet number (the ratio of shear and thermal motions), including the crossover regime. We successfully measure rheological properties near the critical volume fraction(s). We then further measure how their yield stress change with volume fraction.