Component dynamics in miscible blends: Equally and unequally entangled polyisoprene/polyvinylethylene

Miscible blends of 1,4-polyisoprene (PIP) and polyvinylethylene (PVE) are studied using rheo-optical methods to extract the dynamics of each component in the blend. Since orientational coupling contributes to the birefringence, but not the stress, simultaneous analysis of these observables for bidisperse blends is used to determine the coupling coefficient, epsilon. No systematic dependence of epsilon on composition or temperature was detected. The dynamics of the blend components extracted using the mean value of epsilon are in good agreement with those observed previously for equally entangled blends: blending causes only small changes in the component entanglement molecular weights but dramatically alters the species' friction coefficients, with the dynamics of the high T-g species (PVE) being more sensitive to both temperature and composition.