Phase separation and viscoelastic ripening in crosslinked networks

The process of phase separation in elastic solids and viscous fluids is of fundamental importance to the stability and function of soft materials. We explore the dynamics of phase separation and domain growth in a viscoelastic material such as a polymer gel. Using analytical theory and Monte Carlo simulations we find a new domain-growth regime where the domain size increases as a power law, with a ripening exponent α that depends on the viscoelastic properties of the material. For example, α = 1 in a Maxwell material, which is markedly different from the well-known Ostwald ripening process with α = 1/3. We generalize our theory to systems with arbitrary power-law relaxation behavior and discuss our findings in the context of the long-term stability of materials and recent experimental results on phase separation in cross-linked networks and cell cytoskeleton.