This research is an experimental and theoretical study on the viscoelastic properties of blends of dissimilar polymers in the entangled fluid state. Binary blends will first be prepared from well-characterized linear polybutadienes of narrow molecular-weight distribution and variable microstructure. The heteropolymer character of these mixtures will be controlled by increasing the disparity of the vinyl group content in the participating components. Dynamic-oscillatory, steady-shear, tensile, and step- strain experiments will be utilized in examining the linear and nonlinear viscoelasticity of these systems at several temperatures as a function of composition. The fluidity, elasticity, and rigidity of a blend will thus be related to the corresponding properties of its pure constituents. Blends of commercial polymers will also be investigated to test whether the conclusions drawn on model polymer mixtures apply to cases of commerical interest. Especial emphasis will be given on blends where miscibility is driven by the presence of strong specific interactions. A molecular theory already developed to explain the composite network architecture and molecular dynamics in miscible heteropolymer blends will be extended to accommodate non-ideal behavior. This research is part of a general format to understand better the mixing behavior of dissimilar polymer. A particle outcome would be more efficient processing of recycled plastics, which are typically mixtures.
