Effect of patterned surface on diblock-copolymer melts and polymer blends near the critical point

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Abstract
We investigate the density profile of diblock-copolymer melts and polymer blends close to a patternedsurface. For diblocks we find a dependence of the orientation of the polymer chains and the lamellae on the ratio of the natural bulk period to the pattern period L. For a very large pattern period, the diblocks experience locally a homogeneous surface and orient perpendicular to it. For commensurable periods, their orientation is parallel and the lamellae are perpendicular to the surface. A sudden change in orientation is seen at a ratio R g /L= 2∛ /2π for symmetric diblocks, where R g is the radius of gyration of the diblock in the disordered melt. Polymer blends always follow the surfacepattern close to the surface if the surfaceinteraction is strong enough.