DYNAMICS OF EACH COMPONENT IN MISCIBLE BLENDS OF POLYISOPRENE AND POLYVINYLETHYLENE

The dynamics of the individual components in 1,4-polyisoprene/polyviny lethylene (PIP/PVE) miscible blends are studied using dynamic stress-o ptical measurements. While the homopolymers are thermorheologically si mple and obey the stress-optic rule, the blends show failure of time-t emperature superposition and complex stress-optic behavior. The way in which the stress-optic rule fails reveals the relaxation dynamics of each species. The dynamic modulus and complex birefringence coefficien t are analyzed to infer the relaxation of each component. The entangle ment molecular weight, M(e), and monomeric friction coefficient, zeta0 , of each species as a function of blend composition and temperature a re determined from the contribution of each species to the dynamic mod ulus. The effect of blending on M(e) of each component is small; howev er, its effect on zeta0 of each species is dramatic. Blending strongly speeds the rate of relaxation of the high T(g) component (PVE), while more modestly slowing the relaxation of the low T(g) component (PIP). The dynamics of each species have different temperature dependencies in the blend, which leads to the failure of the superposition principl e. Furthermore, both the difference between the friction coefficients of the two species and the difference in their temperature dependencie s is greater in blends rich in the high T(g) material (PVE).