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.


This document is the Accepted Manuscript version of a Published Work that appeared in final form in Macromolecules, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: http://pubs.acs.org/doi/full/10.1021/ma102156p


transient network, fracture, nonlinear, flow, shear start-up, shear banding, strain hardening, sliding friction, instabilities, associating polymers, failure-mode transition

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