Surface-directed spinodal decomposition modified by a surface active copolymer

We have studied the surface-induced spinodal decomposition in thin films of deuterated and protonated polystyrene, using 3He nuclear-reaction analysis and dynamic secondary-ion mass spectroscopy. We found that the amplitude of this process may be modified by a polyisoprene-polystyrene diblock copolymer, which segregates predominantly to the surface when admixed to the isotopic polystyrene blend. This is due to the reduced surface attraction of deuterated polystyrene for the increased surface coverage by diblocks. Finally, the surface directed mode of the spinodal decomposition is observed to be extinct for the surface completely covered by copolymers.