ABSTRACT:Flow effects on the structure and the related viscoelastic properties of lamellar forming poly(styreneblock-2-vinylpyridine)s (SP) and DP in which S in SP replaced by deutrated chains are studied by small angle neutron scattering (SANS) and viscoelastic measurements under shear flows near the order-disorder transition (ODT). A distinctive feature of this sample is that both components have quite similar viscoelastic properties. In the quiescent ordered states, SANS intensities showed strong anisotropy denoting flow-induced alignment of lamellar structure at high shear rates ( _ ) in a limited range of concentration. When the lamellae are well aligned, first normal stress difference was proportional to _ 2 and reduced steady state compliance J eR became practically the same as those of components. The viscosity behaviors in the quiescent ordered and disordered states were also the same as those of components. In the disordered states, on the other hand, J eR was higher than those of components. Under steady shear flows, however, SANS intensities are isotropic and became lower and J eR became almost the same as those of components denoting the suppression of fluctuation effects. Block copolymers possess different microphaseseparated structure in the ordered states, such as sphere, cylinder, co-continuous and lamella, depending on the molecular structure and compositions of components. In the disordered states but near the order-disorder transition (ODT), there exist composition fluctuations of component polymers in the block copolymer liquids. Both the microphase separated structure and the composition fluctuations affect the rheological properties of block copolymers, therefore, structure and the related viscoelastic properties of the block copolymers have been extensively studied both in the ordered and the disordered states. General results of rheological properties for variety of block copolymers are summarized in review articles.

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