Effects of droplet deformability on emulsion rheology

Shear viscosities of sodium dodecylsulfate (SDS) stabilized, deformability controllable polydimethylsiloxane (PDMS) emulsions are reported over a wide volume fraction range (0.01–0.72). Droplet deformability dependent shear thinning behavior is observed as the volume fraction increases. Shear viscosities at a shear rate of 1000 s−1 are converted into relative viscosity versus volume fraction curves and comparison with the Krieger–Dougherty equation for hard spheres has allowed determination of the critical deformation volume fraction. “Hard” droplets deform at the colloidal glass transition volume fraction (ϕg), whereas “soft” droplets deform at volume fractions well below ϕg. New insight into the role of droplet deformability on emulsion rheology is achieved.