Model physically associating solutions of acrylic triblock copolymer molecules in a midblock-selective solvent displayed non-linear strain-stiffening behavior which transitioned to rapid strain softening during shear start-up experiments at reduced rates spanning almost four orders of magnitude. Softening was believed to result from the shear-induced formation of highly localized regions of deformation in the macromolecular network. This behavior was accurately captured by a model that incorporated the strain energy and relaxation behavior of individual network strands in the solution. Flow curves predicted from the model were non-monotonic, consistent with the onset of flow instabilities at high shear rates. The non-linear stress response reported here, coupled with the wide range of accessible relaxation times of these thermoreversible solutions, makes them ideal model systems for studies of failure-mode transitions in physically associating solutions and gels.
transient network, fracture, nonlinear, flow, shear start-up, shear banding, strain hardening, sliding friction, instabilities, associating polymers, failure-mode transition
Date of this Version
Erk, Kendra and Shull, Kenneth R., "Rate-Dependent Stiffening and Strain Localization in Physically Associating Solutions" (2011). School of Materials Engineering Faculty Publications. Paper 1.