Cylindrical phase of block copolymers: Stability of circular configuration to elliptical distortions and thin film morphologies

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Abstract
We study the cylindrical phase of a diblock copolymer melt in the strong segregation limit, and initially examine the stability of this morphology against elliptical perturbations. Surprisingly, we find that an elliptical conformation of the columns has lower free energy than a circular one. The size of the ellipse’s eccentricity depends on f, the minority block fraction. We proceed to examine the morphology of the melt when placed between two hard, flat surfaces. The columns can either form with their axes in the plane of the bounding surfaces (denoted parallel) or with their axes perpendicular to the bounding surfaces. We determine when the parallel alignment is preferred over the perpendicular alignment.