Mechanical and dielectric measurements in polymers: Differences in time-temperature superposition behavior

Comparison of rheological measurements made on a series of polybutadienes of different microstructures using dielectric measurements is presented. Time domain dielectric spectroscopy is used to obtain the dielectric response on a large dynamic range. The temperature dependences of the characteristic times are identical for both dielectric and mechanical responses within the experimental uncertainties of the measurements. The dynamic range of rheological experiments can be extended to higher frequencies in order to fully analyze the possible identity of the temperature dependences of dielectric and mechanical relaxations.