Probing Shear-Banding Transitions of Entangled Liquids Using Large Amplitude Oscillatory Shearing (LAOS) Deformations.

We explore the dynamical response, under Large Amplitude Oscillatory Shear (LAOS) deformation, of a new class of constitutive models (denoted generically VCM) designed to describe entangled solutions of wormlike micellar solutions or concentrated polymer solutions. The goal is to investigate the applicability of LAOS as a test protocol for determining the rheological properties of entangled fluids and the onset of shear banding events that are observed experimentally. The VCM family of models show that shear-banding transitions will develop in LAOS experiments at a frequency-dependent critical strain. The velocity and stress field exhibit a complex dynamical response that varies with both the frequency and amplitude of the forcing. The rheological response of the different states that are observed can be represented in terms of a Pipkin diagram together with Lissajous figures (phase plane portraits). [ABSTRACT FROM AUTHOR]