Direct Measurement of Molecular Mobility in Actively Deformed Polymer Glasses

Condensed Matter journal club

Direct Measurement of Molecular Mobility in Actively Deformed Polymer Glasses

  • Event time: 11:30am
  • Event date: 4th February 2011
  • Speaker: Mike Cates (Formerly School of Physics & Astronomy, University of Edinburgh)
  • Location: Room 2511,

Event details

Abstract

When sufficient force is applied to a glassy polymer, it begins to deform through movement of the polymer chains. We used an optical photobleaching technique to quantitatively measure changes in molecular mobility during the active deformation of a polymer glass [poly(methylmethacrylate)]. Segmental mobility increases by up to a factor of 1000 during uniaxial tensile creep. Although the Eyring model can describe the increase in mobility at low stress, it fails to describe mobility after flow onset. In this regime, mobility is strongly accelerated and the distribution of relaxation times narrows substantially, indicating a more homogeneous ensemble of local environments. At even larger stresses, in the strain-hardening regime, mobility decreases with increasing stress. Consistent with the view that stress-induced mobility allows plastic flow in polymer glasses, we observed a strong correlation between strain rate and segmental mobility during creep
SCIENCE 323 (9) 231-234 (2009)

Authors

Hau-Nan Lee, Keewook Paeng, Stephen F. Swallen, M. D. Ediger