Component Dynamics in Polyisoprene/Poly(4-tert-butylstyrene) Miscible Blends

Abstract

Linear viscoelastic and dielectric behavior was examined for blends of cis-polyisoprene (PI-20; MPI = 19.9 × 103) and poly(4-tert-butylstyrene) (PtBS-16; MPtBS = 16.4 × 103) with the PtBS concentration of wPtBS = 30 and 50 wt %. At temperatures examined, T ≤ 120 °C, the PI/PtBS blends were in a statically homogeneous state. Since PI had the type-A dipole while PtBS did not, the dielectric loss of the blends measured at low angular frequencies ω (<105 s−1) was attributed exclusively to the global motion of PI chains. At low T and/or high wPtBS, the dielectric loss data of the PI chains did not obey the time−temperature superposition, despite the static homogeneity in the blends. Comparison of the viscoelastic and dielectric data indicated that in the blends PtBS relaxed more slowly than PI. Thus, PtBS possibly gave an effectively quenched, nonuniform frictional environment in the time scale of the global relaxation of PI, and changes of this frictional nonuniformity with T appeared to result in the failure...