Viscoelasticity of a simple liquid mixture during spinodal decomposition

We report measurements of the effective viscosity and elasticity of a critical mixture of isobutyric acid and water in the process of phase separation under shear. The viscoelasticity of the sheared sample is a consequence of capillary forces associated with domain interfaces that produce linear domain growth in quiescent samples. We find agreement with a theory recently proposed by Doi and Ohta and obtain an estimate of the interfacial area per unit volume during spinodal decomposition.