DYNAMICS OF A ROUSE SEGMENT AS PROBED BY DEPOLARIZED PHOTON-CORRELATION AND VISCOELASTICITY MEASUREMENTS

A polystyrene melt, whose molecular weight (weight-average molecular w eight = 1050) is about that estimated for a Rouse segment;, has been s tudied with depolarized photon-correlation and viscosity measurements. Theoretically the dynamic depolarized light scattering is shown to be affected by the reorientational motion of the whole polymer molecule in the long-time region and the local segmental motions in the short-t ime region. The elastic dumbbell model is used to describe the viscoel asticity and reorientational motion of the polymer molecule. Relaxatio n times [tau] and tau(v) are extracted from the depolarized light scat tering and viscosity measurement results, respectively. The ratio tau( v)/[tau], being independent of temperature as expected, is of the orde r of magnitude predicted from the theoretical analysis. We come to a s imilar conclusion supporting the above results by analyzing the depola rized photon-correlation results and the viscoelastic relaxation data in the glass-rubber transition zone of entangled polystyrene melts, wh ich are available in literature.