Singlet and triplet transient grating experiments have been used to measure rotational correlation functions for anthracene and 9,10-dimethylanthracene in cis-polyisoprene from Tg+120 °C to Tg+20 °C. Over this temperature range, the rotational correlation time varies by seven decades and follows the temperature dependence of the bulk viscosity. The observed correlation functions are not consistent with predictions of the anisotropic rotational diffusion model. The observed correlation functions for anthracene are consistent with a change in the predominant axis for rotational diffusion as a function of temperature. At high temperatures, in-plane rotation occurs most rapidly, while at low temperatures rotation about the long axis predominates.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.