Lifetime of spatially heterogeneous dynamic domains in polystyrene melts

A photobleaching method is used to measure the rotational dynamics of tetra cene and rubrene in polystyrene, and to determine the lifetime of spatially heterogeneous dynamic domains in the polystyrene matrix. It is possible to selectively photobleach subsets of probe molecules in more mobile environm ents and to measure the time required for the remaining slower-than-average probes to be redistributed into an equilibrium set of environments. For po lystyrene, this exchange time is much longer than the alpha-relaxation time at temperatures very near T-g and exhibits a strong temperature dependence . These results are qualitatively consistent with previous studies on tetra cene in supercooled o-terphenyl and indicate that the observation of long-l ived heterogeneous dynamic domains at temperatures very near T-g is neither matrix nor probe specific. (C) 2000 American Institute of Physics. [S0021- 9606(00)50915-5].