Halato-Telechelic Polymers. 8. Dependence of the Viscoelastic Behavior on the Prepolymer Molecular Weight

The viscoelastic behavior of halato-telechelic polymers (HTP) depends largely on the prepolymer molecular weight, as evidenced by magnesium α,ω-dicarboxylatopolydienes at 296 K. At carboxylato group contents lower than 0.7 mol % ([formula omitted] > 2 × 104), the relaxation of the long and entangled polymeric backbone obeys a WLF type of temperature dependence. The ionic interactions act essentially as thermoreversible cross-links responsible for a dramatic extension of the rubber-like plateau. The time-temperature reducibility disappears at increasing ion concentration, because of the occurrence of a further relaxation characteristic of the ionic component. At sufficiently short prepolymer length ([formula omitted] = 4600 for polybutadiene), the relaxation of the ionic aggregates is only evidenced with an Arrhenius type of activation. It results that the ion aggregation depends not only on the electrostatic interactions (nature of the ion pairs and polarity of the medium) but also on the ion content and the extent of entanglement of the polymeric backbone (considered above its Tg). © 1983, American Chemical Society. All rights reserved.