Dewetting-Induced Alignment and Ordering of Cylindrical Mesophases in Thin Block Copolymer Films

The fabrication of ordered self-assembled nanopatterns in block copolymer films, especially aligned nanostructures, has gained considerable attention. Here, we present a simple approach based on dewetting-induced alignment of cylindrical mesophases in thin polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films. In the course of dewetting enabled by solvent vapor annealing, cylinders aligned parallel to the dewetting contact line with the size of the ordered domain increasing in the direction normal to the dewetting front. The alignment of cylindrical mesophases was driven by the dewetting flow field and by minimization of the elastic energy of the P2VP cylinders in a confined space. We observed a power-law increase of the orientation parameter (f) for the P2VP cylinders with increasing time (t) of hole growth: f ∼ t^1/3. Arrays of precisely aligned cylinders were achieved in long filaments generated by the coalescence of adjacent dewetting holes.