Undulation instability in block-copolymer lamellae subjected to a perpendicular electric field

We examine the stability of lamellar stacks in the presence of an electric field, E0, applied normal to the lamellae. Calculations are performed with self-consistent field theory (SCFT) supplemented by an exact treatment of the electrostatic energy for linear dielectric materials. The calculations identify a critical electric field, E 0, beyond which the lamellar stack becomes unstable with respect to undulations. This E 0 rapidly decreases towards zero as the number of lamellae in the stack diverges. Our quantitative predictions for E 0 are consistent with previous experimental measurements by Xu and co-workers.