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Phys. Rev. Lett. 79, 103–106 (1997)

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

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David B. Hall1, Ali Dhinojwala1, and John M. Torkelson1,2
1Department of Chemical Engineering, Northwestern University, Evanston, Illinois 60208-3120
2Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3120

Received 10 March 1997; published in the issue dated 7 July 1997

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.

© 1997 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.79.103
DOI:
10.1103/PhysRevLett.79.103
PACS:
66.30.Jt, 61.41.+e, 64.70.Pf