Evaporation-Induced Self-Assembly of Diblock Copolymer Films in an Electric Field: A Simulation Study

The self-assembly of cylinder-forming diblock copolymer solutions in the course of solvent evaporation in the presence of an electric field is studied by particle-based simulations. The electric field provides additional control of the evaporation-induced self-assembly (EISA) and enlarges the processing window, which results in the desired formation of cylindrical domains that are perpendicularly oriented to the film surface. Two effects of the electric field are highlighted: (i) If the components of the AB block copolymer exhibit different permittivities, dielectrophoretic forces align the internal AB interfaces along the electric field, rendering parallel cylinders unstable. (ii) If shallow density gradients in the course of EISA give rise to the unfavorable morphology of perpendicular cylinders and subjacent layers of spherical micelles, the application of an electric field results in an elongation of the cylindrical domains and suppresses sphere formation. The beneficial effect of an electric field can be rationalized by the layer evolution model (LEM), previously developed for EISA in the absence of an electric field.