Phase inversion and viscoelastic properties of phase-separated polymer blends

Summary The morphologies and viscoelastic properties of the phase-separated poly(styrene-co-maleic anhydride)/poly(methyl methacrylate) bends have been investigated using TEM and rotational rheometry. Various rheological criteria based on the viscoelastic properties of the blends have been used to evaluate the phase inversion. By correlating the rheological results to data from morphological analysis by TEM, it is found that the maximum of the storage modulus and the viscosity at low shear rate are most suitable for determining the phase-inversion composition of the present phase-separated polymer blends. While the data from the maximum of the shear viscosity at high shear rate and from the shear-thinning extent proposed by Ziegler et al. slightly deviate from that from TEM micrograph, which indicates that shear-induced structure lie. Moreover, the prediction using various rheological models, as the viscosity ratio of the two coexisting phases is substituted for that of the pure components, is in nearly good agreement with that from TEM observation.