Viscoelastic and Dielectric Behavior of a Polyisoprene/Poly(4-tert-butyl styrene) Miscible Blend

Abstract

Linear viscoelastic and dielectric measurements were conducted for a blend of polyisoprene (PI, M = 19.9 × 103) and poly(4-tert-butyl styrene) (PtBS, M = 69.5 × 103) with a PI/PtBS composition of 8/2 (w/w). In general, PI and PtBS exhibit the lower-critical-solution-temperature (LCST) type phase behavior. At temperatures examined, T ≤ 70 °C, our PI/PtBS blend was in a statically homogeneous state. The PI chain has the so-called type-A dipoles parallel along the backbone, and its large-scale (global) motion activates prominent dielectric relaxation, while the PtBS chain has no type-A dipoles and its global motion is dielectrically inert. In fact, at angular frequencies ω between 101 s-1 and 105 s-1 and at T ≤ 70 °C, the dielectric signal of the blend was exclusively attributed to the PI chains therein. The time−temperature superposition failed for the dielectric loss e‘ ‘ of the PI chains, despite the fact that the blend was statically homogeneous. This result suggested that the frictional environment for ...