Rotational Dynamics of a Probe in Rubbery Polymers Characterized by Time-Resolved Fluorescence Anisotropy Measurement

The rotational relaxation time (τrot) of a fluorescent molecule, coumarin 153 (C153), dispersed in different rubbery polymers is characterized by time-resolved fluorescence anisotropy measurement, and an attempt is made to quantitatively combine it with the segmental relaxation time (τseg) of the corresponding matrix polymer obtained by dielectric relaxation spectroscopy. This study here demonstrates that τseg extrapolated to higher temperatures using the Vogel–Fulcher–Tammann law can be superimposed on τrot, resulting in a single curve. This behavior is common for polymers with different glass transition temperatures such as polyisoprene and acrylonitrile/butadiene copolymer, implying that the rotational dynamics of C153 is a useful tool for the characterization of polymer dynamics.