Scaling Properties of Gelling Systems in Nonlinear Shear Experiments

TL;DR

This study investigates the nonlinear shear rheology of near-critical polymer gelling systems, revealing self-similar stress overshoot behavior and power-law relaxation, indicating mesoscopic dynamics related to gelation extent.

Contribution

It demonstrates the self-similarity of stress overshoot and power-law relaxation in gelling systems, linking rheological features to gelation proximity and mesoscopic dynamics.

Findings

Stress overshoot exhibits self-similarity across shear rates.

Post-flow stress relaxation follows a power law.

Relaxation time depends on prior shear rate.

Abstract

We study model near-critical polymer gelling systems made of gluten proteins dispersions stabilized at different distances from the gel point. We impose different shear rates and follow the time evolution of the stress. For sufficiently large shear rates, an intermediate stress overshoot is measured before reaching the steady state. We evidence self-similarity of the stress overshoot as a function of the applied shear rate for samples with various distances from the gel point, which is related to the elastic energy stored by the samples, as for dense systems close to the jamming transition. In concordance with the findings for glassy and jammed systems, we also measure that the stress after flow cessation decreases as a power law with time with a characteristic relaxation time that depends on the shear rate previously imposed. These features revealed in non-linear rheology could be the signature of a mesoscopic dynamics, which would depend on the extent of gelation.