Linear and nonlinear viscoelasticity of water-in-oil emulsions: Effect of droplet elasticity

The effect of droplet elasticity on the linear and nonlinear viscoelasticity of water-in-oil emulsions was studied by comparing two kinds of emulsions: one with pure water as droplets, the other with a suspension of hectorite clay as droplets. The clay-filled emulsion had high droplet elasticity due to the gelation of the clay suspension. As the water-to-oil volume ratio ϕ increased, the emulsions changed from liquid-like state to solid-like state as the droplets formed a jammed state. Effect of droplet elasticity was most significant in the jammed state, where the clay-filled emulsion showed a much higher plateau modulus than the clay-free one. Nonlinear viscoelasticity was observed by the large amplitude oscillatory shear (LAOS) rheology. The Lissajous curve was dissected into the cage-yielding and cage-restructuring parts, and the cage modulus Gk in the nonlinear viscoelastic regime was higher for clay-filled emulsion than the clay-free one in the jammed state due to the contribution of the droplet elasticity. The droplet elasticity was found to contribute to the nonlinear viscoelasticity of the emulsions.