BREAKDOWN OF THE ROUSE MODEL FOR POLYMERS NEAR THE GLASS-TRANSITION TEMPERATURE

The bead-spring model pioneered by Rouse is generally considered to be the basis of polymer physics. We show generally that it breaks down dramatically near the glass transition temperature by shear creep measurements on several polymers with very different backbone structures. The physical origin of this breakdown is traced to the segmental relaxation time having a much stronger temperature dependence than that of the Rouse spectrum. This property, a consequence of the cooperative nature of segmental relaxation in dense packed polymers, was predicted before by a coupling model. We verify this property directly by dielectric relaxation measurements with a wide frequency window of ten decades.