|Title||Molecular Mobility of Poly (methyl methacrylate) Glass During Uniaxial Tensile Creep Deformation|
|Publication Type||Journal Article|
|Year of Publication||2009|
|Authors||Lee, H. N., K. Paeng, S. F. Swallen, M. D. Ediger, R. A. Stamm, G. A. Medvedev, and J. M. Caruthers|
|Journal||Journal of Polymer Science Part B-Polymer Physics|
|Keywords||AMORPHOUS POLYMERS, DIELECTRIC-RELAXATION, DYNAMICS, ENHANCED TRANSLATIONAL DIFFUSION, FLUORESCENCE, glassy polymers, mechanical properties, MODEL, NONLINEARLY VISCOELASTIC BEHAVIOR, POLYCARBONATE, POLYMER GLASSES, SEGMENTAL, spatially heterogeneous dynamics, TEMPERATURE-DEPENDENCE, THERMODYNAMICALLY CONSISTENT, yielding|
An optical photobleaching method has been used to measure the segmental dynamics of a poly(methyl methacrylate) (PMMA) glass during uniaxial creep deformation at temperatures between T(g) - 9 K and T(g) - 20 K. Up to 1000-fold increases in mobility are observed during deformation, supporting the view that enhanced segmental mobility allows flow in polymer glasses. Although the Eyring model describes this mobility enhancement well at low stress, it fails to capture the dramatic mobility enhancement after flow onset, where in addition the shape of the relaxation time distribution narrows significantly. Regions of lower mobility accelerate their dynamics more in response to an external stress than do regions of high mobility. Thus, local environments in the sample become more dynamically homogeneous during flow.
|Alternate Journal||J Polym Sci Part B: Polym Phys|