Influence of segmental swelling ratio of a symmetric block copolymer on the morphology of melt-mixed immiscible polymer blends

We investigate droplet breakup and coalescence under shear flow for an immi scible polymer blend system in which styrene-acrylonitrile random copolymer and poly(cyclohexyl methacrylate) are the blend components, and a symmetri c poly(styrene-b-methyl methacrylate) block copolymer (bcp)is utilized as a compatibilizer. The influence on the blend morphology of the ratio (S-r) b etween the swelling : power at the interface of the bcp segment outside the droplet versus that inside the droplet is studied. We fmd that the balance of swelling between external and internal segments has an important, influ ence on the ultimate blend morphology. Four zones of morphological behavior s are observed: S-r < 0.4, internal emulsification failure; 1 > S-r > 0.4, unstable emulsification; 2.5 > S-r > 1, stable emulsification; S-r > 2.5, e xternal emulsification failure.