Thin films of perpendicularly oriented diblock copolymers: Lamellar distortions driven by surface-diblock interfacial tensions

We consider the problem of a diblock copolymer melt thin film on a homogeneous nat surface or confined between two flat plates. When there is significant mismatch between the film thickness and an integer multiple of the lamellar spacing, perpendicular orientation of the lamellae may be observed. However, because of differences in the interfacial tensions between the surface and the two blocks, the lamellae may be distorted, from a straight interface to a curved interface. We examine theoretically this distortion and show that its amplitude may only be a few percent of the lamellar spacing.