  We report Monte Carlo simulations of a lattice-polymer model that can account
for both polymer crystallization and liquid-liquid demixing in solutions of
semiflexible homopolymers. In our model, neighboring polymer segments can have
isotropic interactions that affect demixing, and anisotropic interactions that
are responsible for freezing. However, our simulations show that the isotropic
interactions also have a noticeable effect on the freezing curve, as do the
anisotropic interactions on demixing. As the relative strength of the isotropic
interactions is reduced, the liquid-liquid demixing transition disappears below
the freezing curve. A simple, extended Flory-Huggins theory accounts quite well
for the phase behavior observed in the simulations.
