We investigate symmetric grain boundaries in a lamellar diblock copolymer
system. The form of the interface between two grains strongly depends on the
angle θ, between the normals of the grains. When this angle is small,
the lamellae transform smoothly from one orientation to the other, creating the
chevron morphology. As θ increases, a gradual transition is observed to
an omega morphology characterized by a protrusion of the lamellae along the
interface between the two phases. We present a theoretical approach to find
these tilt boundaries in two-dimensional systems, based on a Ginzburg-Landau
expansion of the free energy. Calculated order parameter profiles and energies
agree well with transmission electron microscope experiments, and with full
numerical solution of the same problem.Comment: 11 pages, 10 gzipped postscript and jpeg figures, published in PRE
Vol. 61, March 200