Recovery rheology via rheo-SANS: Application to step strains under out-of-equilibrium conditions

Johnny C.W. Lee, Lionel Porcar, Simon A. Rogers

Research output: Contribution to journalArticlepeer-review


Stress relaxation from a step strain test provides important information about constituent dynamics, but if a material has experienced a complex shear history, the underlying physics is not straightforward to access. We use recovery rheology and rheo-small-angle neutron scattering to probe the nonlinear dynamics of an entangled wormlike micelle solution by applying step strains after complex shear histories enforced by large-amplitude oscillatory shear (LAOS) flow. We show that a universal relaxation modulus can be obtained from step strain tests with complex shear histories, as long as the modulus is defined in terms of the recoverable strain. The shear and normal stresses, as well as the alignment of micellar Kuhn segments, are shown to be positively correlated with the recoverable strain. We identify re-entanglement of polymeric chains after cessation of LAOS and show that this process occurs over the same timescales as linear-regime stress relaxation. This work, therefore, lays the foundation of how to accurately probe out-of-equilibrium rheology in a consistent manner.

Original languageEnglish (US)
Article numbere16797
JournalAIChE Journal
Issue number12
StatePublished - Dec 1 2019


  • LAOS
  • entanglement
  • nonlinear rheology
  • polymers rheology
  • rheo-small-angle neutron scattering
  • step strain
  • stress relaxation

ASJC Scopus subject areas

  • Biotechnology
  • Environmental Engineering
  • General Chemical Engineering


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