POLYMER ALLOYS BASED ON POLY(2,6-DIMETHYL-1,4-PHENYLENE ETHER) AND POLY(STYRENE-CO-ACRYLONITRILE) USING POLY(STYRENE-B-(ETHYLENE-CO-BUTYLENE)-B-METHYL METHACRYLATE) TRIBLOCK COPOLYMERS AS COMPATIBILIZERS

Poly(styrene-b-(ethylene-co-butylene)-b-methyl methacrylate) (P(S-b-EB-b-MMA) triblock copolymers containing various amounts of the elastomeric center block (6-38 wt % PEB) have been used to compatibilize polymer blends based on poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(styrene-co-acrylonitrile) (PSAN). From the dynamic mechanical analysis in combination with transmission electron microscopy detailed information about the location of the block copolymers is obtained, because the intermixing of the PS block with PPE and the PMMA block with PSAN changes the glass transitions of the main components. In all studied blends, the PS block penetrates into the PPE. In blends with PSAN20, a copolymer containing 20 wt % acrylonitrile, the PMMA block is mixed with PSAN, while this is not the case in blends with PSAN43 (43 wt % acrylonitrile). In blends with PSAN20 the elastomeric center block (PEB) does not form a rubbery layer along the PPE/PSAN interface. Due to the large incompatibility between PEB and all other blend components small rubber islands form at the PPE/PSAN boundary, giving rise to a ''raspberry'' type morphology. The location of these rubbery particles at the interface causes a considerable improvement of the mechanical interfacial strength. Stable bicontinuous morphologies are formed at PSAN:PPE ratios around 60:40.