A comparison of phase separation in gels using different elastic models

Phase separation in gels can occur in several different geometries, which can be roughly categorized as one, two, or three dimensional. Here we calculate candidate phase diagrams for five elastic models in the three geometries and show that finite extensibility can lead to anomalous-looking phase diagrams because of extreme stretching induced at high solvent fraction. We also show that neo-Hookean elasticity cannot support phase separation in certain cases. We apply our finding to recent experiments as well as gels with two solvents.