DECOUPLING OF TIME SCALES OF MOTION IN POLYBUTADIENE CLOSE TO THE GLASS-TRANSITION

Studying the dynamic structure factor of polybutadiene in the first valley of S(Q) we decoupling of microscopic and macroscopic time scales about 40 K above T(g). At higher temperatures the time scale set by the viscosity scales with the microscopic scale, while at lower T strong decoupling effects occur. We present evidence that the decoupled low-temperature relaxation is distinctly different from the high-frequency "beta-process." The decoupling temperature coincides with the critical temperature of the mode coupling theory.