Spinodal decomposition in thin films of a polymer blend

Spinodal decomposition in thin films of a blend of deuterated polystyrene and poly(styrene-co-4-bromostyrene) was studied with time-of-flight--elastic-recoil detection and light microscopy. We found different demixing behavior, depending on whether the films were prepared on the oxide layer of a silicon wafer or on a chromium-plated one. On the latter surface a bilayer of the two bulk phases is formed, whereas on the oxide layer a domain structure remains. The formation of the bilayer is ascribed to the complete wetting of each surface by the corresponding, preferentially adsorbed component.