Diblock copolymer melts in electric fields: The transition from parallel to perpendicular alignment using a capacitor analogy

We consider alignment of a symmetric diblock copolymer melt thin film or bu lk phase by an electric field using a capacitor analogy. For the lamellar p hase we show that alignment of the lamellae in the direction perpendicular to the bounding electrodes, compared to parallel alignment, occurs for thic ker films. For thin films the critical electric field required for a transi tion from parallel to perpendicular alignment is proportional to H-1/2, whe re H is the film thickness. We also consider the possibility of a mixed lam ellar morphology where, because the bounding electrodes prefer one block, p arallel layers form adjacent to the electrodes, while in the interior regio n there is perpendicular alignment. We determine the conditions for such a morphology.