VISCOSITY DEPENDENCE OF THE LOCAL SEGMENTAL DYNAMICS OF ANTHRACENE-LABELED 1,2-POLYBUTADIENE IN DILUTE-SOLUTION

Time-correlated single-photon-counting measurements have been performe d on anthracene-labeled 1,2-polybutadiene. The local segmental dynamic s were observed in seven solvents covering a viscosity range of more t han three decades and over the temperature range of 280-350 K. Correla tion times were extracted from the fluorescence anisotropy decays and were determined as a function of temperature in all solvents. The obse rved temperature and viscosity dependence has been examined in terms o f Kramers' theory in the high friction limit and two empirical equatio ns, those of Fleming and co-workers and Robinson, both of which incorp orate the idea of frequency-dependent friction developed by Grote-Hyne s. It was found that the dynamics scaled as the viscosity to the power 0.82 +/- 0.04.