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 d ramatically near the glass transition temperature by shear creep measu rements on several polymers with very different backbone structures. T he physical origin of this breakdown is traced to the segmental relaxa tion time having a much stronger temperature dependence than that of t he Rouse spectrum. This property, a consequence of the cooperative nat ure of segmental relaxation in dense packed polymers, was predicted be fore by a coupling model. We verify this property directly by dielectr ic relaxation measurements with a wide frequency window of ten decades .