  Self-Consistent Field Theory is applied to a film of cylindrical-forming
block copolymer subject to a surface field which tends to align the cylinders
parallel to electrical plates, and to an external electric field tending to
align them perpendicular to the plates. The Maxwell equations and
self-consistent field equations are solved exactly, numerically, in real space.
By comparing the free energies of different configurations, we show that for
weak surface fields, the phase of cylinders parallel to the plates makes a
direct transition to a phase in which the cylinders are aligned with the field
throughout the sample. For stronger surface fields, there is an intermediate
phase in which cylinders in the interior of the film, aligned with the field,
terminate near the plates. For surface fields which favor the minority block,
there is a boundary layer of hexagonal symmetry at the plates in which the
monomers favored by the surface field occupy a larger area than they would if
the cylinders extended to the surface.
