Hierarchical coarsening in the late stage of viscoelastic phase separation

Coarsening is a general phenomenon in phase separating mixtures. In this study, we report a hierarchical coarsening at different length scales. Dispersed domains grew by direct combination of two/three small ones while some small domains can survive for a long time. The small angle laser light scattering showed that the scattered intensity exhibited multiple "decay-growth" transitions in the coarsening process. The evolution of the main peak gave a characteristic power law index of about -3/4, which is much faster than the -1/3 relationship from the traditional theories. We propose that relaxation and hydrodynamic flow play important roles in this process.