SURFACE-DIRECTED SPINODAL DECOMPOSITION MODIFIED BY A SURFACE-ACTIVE COPOLYMER

We have studied the surface-induced spinodal decomposition in thin fil ms of deuterated and protonated polystyrene, using He-3 nuclear-reacti on analysis and dynamic secondary-ion mass spectroscopy. We found that the amplitude of this process may be modified by a polyisoprene-polys tyrene diblock copolymer, which segregates predominantly to the surfac e when admired to the isotopic polystyrene blend. This is due to the r educed surface attraction of deuterated polystyrene for the increased surface coverage by diblocks. Finally, the surface directed mode of th e spinodal decomposition is observed to be extinct for the surface com pletely covered by copolymers.