A series of monodisperse polybutadienes has been used to perform mecha
nical relaxation measurements from the flow regime to the glassy state
. Results on loss shear moduli have been analyzed within the framework
of a coupling model. It has been found to represent well the frequenc
y dependence in the glassy and terminal zones using a segmental motion
coupling parameter beta(alpha) and an entanglement coupling parameter
beta(eta). Moreover, our results on apparent shift factors resulting
from time-temperature superposition are consistent with the lack of th
ermorheological simplicity predicted by the coupling theory due to the
difference between beta(alpha) and beta(eta).