  We study the rheology of monodisperse and bidisperse emulsions with various
droplet sizes (1 $\mu$m -- 2 $\mu$m diameter). Above a critical volume fraction
$\phi_c$, these systems exhibit solid-like behavior and a yield stress can be
detected. Previous experiments suggest that for small thermal particles,
rheology will see a glass transition at $\phi_c = \phi_g =0.58$; for large
athermal systems, rheology will see a jamming transition at $\phi_c = \phi_J
=0.64$. However, simulations point out that at the crossover of thermal and
athermal regimes, the glass and jamming transitions may both be observed in the
same sample. Here we conduct an experiment by shearing four oil-in-water
emulsions with a rheometer. We observe both a glass and a jamming transition
for our smaller diameter droplets, and only a jamming transition for our larger
diameter droplets. The bidisperse sample behaves similarly to the small droplet
sample, with two transitions observed. Our rheology data are well-fit by both
the Herschel-Bulkley model and the Three Component model. Based on the fitting
parameters, our raw rheological data would not collapse onto a master curve.
Our results suggest that liquid-solid transitions in dispersions may not be
universal, but depend on particle type.
