SURFACE PHASE-TRANSITION IN A POLYMER BLEND

When measuring the surface segregation towards the vacuum in films of an asymmetric blend of deuterated polystyrene (dPS) and poly(styrene-4 -co-bromostyrene) (PBr(x)S) (N(dPS) : N(PBrxS) = 3.76) a jump in the s urface excess z of dPS was observed when the binodal of the blend was approached from the one-phase region. This jump can be interpreted as surface phase transition, if gradient terms are included in the bare surface free energy F(S) of the blend. Such gradient terms have been r ecently proposed in theoretical work on polymer blends and surfaces.