2013 Volume 41 Issue 2 Pages 83-91
Viscoelastic properties of symmetric poly(styrene-block-2-vinylpyridine)s in the ordered and disordered states under steady shear flow are examined for relatively low molecular weight samples at melt based on the temperature dependence of interaction parameter χ. Since both components have almost the same viscoelastic properties, data for block copolymers and components are directly compared. In the disordered state near the ODT, two constant values for shear viscosity η, η01 and η02 at lower and higher shear rates, γ, respectively are obtained for diblock samples and η01 coincided with the value obtained by dynamic flow measurements, which are higher than the values for components. The constant values of Je are obtained at γ range where η02 are obtained, which are also higher than those of components. It was concluded that higher η01 and lower η02 values are due to the fluctuation effects and their suppression by the flow with higher γ, respectively. It was also concluded that fluctuation effects on viscoelastic properties completely disappear at around χN < 2 - 3 for SPs. In the ordered state, well aligned state was only attained for the sample having lowest molecular weight. The values of η0 and Je obtained in well aligned state are consistent with those in disordered state, denoting that there is no discontinuity of data due to ODT.
