Viscosity Dependence of the Local Segmental Dynamics of Anthracene-Labeled 1,2-Polybutadiene in Dilute Solution

Time-correlated single-photon-counting measurements have been performed on anthracene-labeled 1,2-polybutadiene. The local segmental dynamics were observed in seven solvents covering a viscosity range of more than three decades and over the temperature range of 280−350 K. Correlation times were extracted from the fluorescence anisotropy decays and were determined as a function of temperature in all solvents. The observed temperature and viscosity dependence has been examined in terms of Kramers' theory in the high friction limit and two empirical equations, those of Fleming and co-workers and Robinson, both of which incorporate the idea of frequency-dependent friction developed by Grote−Hynes. It was found that the dynamics scaled as the viscosity to the power 0.82 ± 0.04.