| Abstract
| - The linear viscoelastic properties of 1,4-polyisoprene (PI;MW = 504 000) were measuredby combined mechanical and dielectric spectroscopies. For localsegmental motion, the respectivemechanical and dielectric relaxation times, although differingsubstantially in magnitude, have identicaltemperature dependencies. The shape of the segmental relaxationfunction itself was sensitive totemperature. The data, obtained over a 160 degree range oftemperatures, could be reduced to yieldostensibly satisfactory master curves; however, detailed analysisreveals the usual breakdown of time−temperature superpositioning in the glass transition zone. Giventhe near equivalence of the respectivebreadths of its terminal and segmental dispersions, thermorheologicalcomplexity in PI is unanticipatedby theory. In the plateau zone, the mechanical spectrum of PIexhibits power law behavior, with anexponent (0.21) close to a proposed universal value.
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