Controlling the phase morphology of immiscible poly(2,6-dimethyl-1,4-phenylene ether)/poly(styrene-co-acrylonitrile) blends via addition of polystyrene.

The microstructure of melt-processed, immiscible poly(2,6-dimethyl-1,4-phenylene ether)/poly(styrene-co-acrylonitrile) blends (PPE/SAN) was controlled by systematically adjusting the viscosity ratio between both phases. For this purpose, low-viscous polystyrene (PS) was added as a third component, as it shows selective miscibility with PPE and thus allows the varying of the shear viscosity of PPE over a broad range. In order to theoretically predict the phase morphology, a model following Utracki was applied taking into account the viscosity ratio and the respective volume contents of each phase. Detailed transmission electron microscopic investigations of the blend morphologies demonstrated excellent agreement with theory. Moreover, quantitative evaluation of the observed microstructures allowed further description of the degree of blend co-continuity. Thus, desirable compositions of the ternary blend systems could be identified which potentially show enhanced properties such as a high heat deflection temperature, an elevated strength, stiffness, and ease of processing. Finally, a optimum (PPE/PS)/SAN blend system that has been optimised regarding the aforementioned properties was compatibilized by polystyrene-b-poly(1,4-butadiene)-b-poly(methyl methacrylate) triblock terpolymers. Due to the interfacial enrichment of the block copolymer, nanostructured blend morphologies were observed. In the view of these results, pathways to control both the micro- and the nanostructure of PPE/SAN blends are derived, potentially useful to enhance the mechanical as well as thermomechanical property profile. [ABSTRACT FROM AUTHOR]