Phase-field modeling of colloid-polymer mixtures in microgravity

We present a theoretical model for colloid-polymer mixtures in a microgravity environment. The addition of polymer to a colloidal suspension induces weakly attractive forces between the colloids and leads to a three-phase coexistence region, wherein a "liquid" phase coexists with a low-density gas phase and a high-density crystal phase. Colloid-polymer mixtures are thus an archetype for modeling phase transition processes, but the details of the observed colloidal structures remain poorly understood. We construct, analyze and numerically simulate a phase-field model for structure evolution in colloid-polymer mixtures. The model consists of the Cahn-Hilliard equation, which describes phase separation processes in multicomponent mixtures, coupled with the Stokes equation for viscous fluid flow. The results of the model will be compared against experiments performed on the International Space Station, using data available on the NASA Physical Sciences Informatics system.