TEMPERATURE-DEPENDENCE OF THE NONERGODICITY PARAMETER IN POLYBUTADIENE IN THE NEIGHBORHOOD OF THE GLASS-TRANSITION

Using neutron-spin-echo and time-of-flight spectroscopy we have investigated the precise temperature dependence of the elastic (nonergodic) fraction in the spectrum of density fluctuations of the glass-forming polymer polybutadiene. With increasing temperature we found a critical decrease of the normalized elastic intensity following closely the (Tc-T)1/2 behavior predicted by the mode-coupling theory. The critical temperature was determined to be Tc=216+1 K, i.e., 35 K above Tg. © 1990 The American Physical Society.