  A coarse-grained model for solutions of polymers in supercritical fluids is
introduced and applied to the system of hexadecane and carbon dioxide as a
representative example. Fitting parameters of the model to the gas-liquid
critical point properties of the pure systems, and allowing for a suitably
chosen parameter that describes the deviation from the Lorentz-Berthelot mixing
rule, we model the liquid-gas and fluid-fluid unmixing transitions of this
system over a wide range of temperatures and pressures in reasonable agreement
with experiment. Interfaces between the polymer-rich phase and the gas can be
studied both at temperatures above and below the end point of the triple line
where liquid and vapor carbon dioxide and the polymer rich phase coexist. In
the first case interfacial adsorption of fluid carbon dioxide can be
demonstrated. Our model can also be used to simulate quenches from the
one-phase to the two-phase region. A short animation and a series of snapshots
help to visualize the early stages of bubble nucleation and spinodal
decomposition. Furthermore we discuss deviations from classical nucleation
theory for small nuclei.
