Dynamics in miscible blends of polyisoprene and poly(p-tert-butyl styrene): thermo–rheological behavior of components

Abstract

Viscoelastic and dielectric properties were examined for miscible blends of moderately entangled cis-polyisoprene (PI) and poly(p-tert-butyl styrene) (PtBS). The dielectric response exclusively detected the global motion of PI chains having type-A dipoles. In most of the blends, PI and PtBS were the fast and much slower components, respectively. In those blends, the dielectric response of PI was thermo–rheologically complex because the slow PtBS chains quenched the dynamic frictional heterogeneity in the time scale of the PI relaxation. In contrast, the viscoelastic response of PtBS was thermo–rheologically simple because the fast PI chains smeared the heterogeneity. Nevertheless, PtBS exhibited no ordinary entanglement relaxation but retarded Rouse-like relaxation attributable to pseudo-constraint release activated by the PI motion. A simple model based on this molecular picture well described the viscoelastic data of the blends.