Polymer Science Faculty Research

Translation-Rotation Paradox for Diffusion in Glass-Forming Polymers: The Role of the Temperature Dependence of the Relaxation Time Distribution

Ali Dhinojwala


Comparisons are made of the translational and rotational diffusion of small-molecule probes in a polymer near its glass transition temperature, Tg. In the rubbery state, 1.1Tg>T>Tg, translational diffusion is much less temperature dependent than rotational reorientation; in a ``quenched'' glass, translation and rotation have similar temperature dependencies. This is explained to be a consequence of the fact that in the rubbery state near Tg the breadth of the polymer relaxation distribution is strongly temperature dependent, while in the quenched glass it is temperature invariant.