Self-assembly of a homopolymer mixture via phase separation

We propose a mechanism for creating lateral order in thin films of a homopolymer mixture via spinodal decomposition in the presence of a laterally structured substrate surface. The system under consideration is a mixture of deuterated polystyrene and partially brominated polystyrene (PBr_xS, x=0.5) spuncast onto different substrates from toluene solution. We demonstrate that periodic stripe-like domain structures can be observed in the polymer films after spinodal decomposition on a periodic array of Cr lines on a H-terminated Si surface. The effect vanishes when the chemistry of the underlying structure is changed, strongly indicating an interface-driven ordering of the polymer film.