Needless to say, polymer chains in melt state exhibit stochastic thermal motion in various length scales. Macroscopically measured dynamic properties of polymer melts are determined by this motion as given averages of the chain conformation. For example, viscoelastic properties reflect the average orientational anisotropy of subchains (stress-sustaining unit), and the optical anisotropy (birefringence) detects the average anisotropy of the orientation of monomeric segments. In addition, for so-called type-A chains having electrical dipoles parallel along the chain backbone, the dielectric properties are determined by the orientational memory of the chain averaged over the end-to-end distance. Thus, the stochastic chain motion is differently averaged in these properties, so that comparison of those properties allows us to resolve some detailed features of the chain motion.

　　Specifically, comparison of the viscoelastic and optical properties has demonstrated two different origins of the viscoelastic stress, torsional and axial anisotropies of the segmental orientation (as revealed by Inoue and Osaki). The proportionality between the stress and axial anisotropy of the segmental orientation is well established as the stress-optical rule. For entangled type-A polymers having high molecular weights, comparison of viscoelastic and dielectric properties has allowed us to resolve the transient feature of the entanglement constraint on the chain motion. Details of these findings will be explained in the lecture.