Polymer immiscibility enhanced by thermal fluctuations toward crystalline order

We report dynamic Monte Carlo simulations of binary polymer blends. The blends exhibit liquid-liquid phase separation influenced by the nearby crystallization of one component. We found that both binodal and spinodal boundaries of liquid-liquid phase separation shift up above the predictions of the mean-field lattice theory. The enhancement of immiscibility can be assigned to the thermal fluctuations toward better parallel order of the crystallizable chains in the blends, which has been neglected in the mean-field theory. This result serves as a theoretical background to explain the related experimental observations.