Dye reorientation as a probe of stress-induced mobility in polymer glasses.
The reorientation of dye molecules can be used to monitor the segmental dynamics of a polymer melt. We utilize this technique to measure stress-induced mobility in a lightly cross-linked poly(methyl methacrylate) (PMMA) glass during tensile creep deformation. At 377 K (18 K below the glass transition temperature Tg), the mobility increased by a factor of 100 during deformation with a stress of 20 MPa. Generally, the mobility increased as the stress, strain, and strain rate increased. After removing the stress, we observed that the enhanced mobility slowly disappeared during strain recovery. At 377 K, when the stress is lower than 11 MPa, almost no mobility enhancement was observed. Once the stress crossed this threshold value, the mobility dramatically increased.
Lee
Hau-Nan
HN
Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Paeng
Keewook
K
Swallen
Stephen F
SF
Ediger
M D
MD