ON THE MACROPHASE AND MICROPHASE SEPARATION OF COMPATIBILIZERS IN IMMISCIBLE POLYMER BLENDS

Macro- and microphase separation of compatibilizing graft copolymers i n melt-mixed polystyrene/polyamide-6 blends was studied by transmissio n electron microscopy and thermal analysis. Three different graft copo lymers with main chains of polystyrene and side chains of poly(ethylen e oxide) were used as additives at various concentrations. The polyami de-6 domain sizes decreased with increasing amounts of compatibilizing graft copolymers in the blends up to a saturation concentration, afte r which no further reduction was noted. Macrophase separation of the g raft copolymers into discrete macrodomains 20-200 nm in size occurred at concentrations equal to or slightly lower than the saturation conce ntration. The macrodomains of the graft copolymers were microphase sep arated, and the sizes and shapes of the microdomains were found to lar gely depend on the graft copolymer structure and composition. As a con sequence of microphase separation, poly(ethylene oxide) crystallinity was noted in blends with sufficiently high macrophase contents. Observ ations of a graft copolymer interphase between the polystyrene matrix and the polyamide-6 domains confirmed that the graft copolymer was pre sent at the blend interfaces in some of the compatibilized blends. (C) 1996 John Wiley & Sons, Inc.