Complex Effects of the External Electric Fields on the Phase Separation of Polymer Blends

The mechanism of phase separation of polymer blends induced by the external electric field is a long-standing unsolved problem. In this work, we have applied the coarse-grained polarizable model developed earlier to simulate the phase separation of polymer blends under a constant external electric field between two nonselective walls which corresponds to the virtual electrode plates with constant charges. It is found that the effect of the electric field on the phase separation depends not only on the second derivative of the permittivity with respect to the component concentration but also on the permittivity, the dielectric contrast, and the component concentration of the blend system. A mean-field theory with an external electric field is successfully applied to explain the origin of the complex effects and shows a quantitative agreement with the simulation. The reasons for the discrepancy between previous theoretical predictions and experimental observations are discussed. Our theoretical result is consistent with that of Orzechowski et al. at the critical concentration. Notably, our theory can give a complete prediction for the phase diagram under an electric field. This work is helpful to comprehensively understand the complex effects of electric fields on the phase separation of multicomponent polymer systems.