Paper Number
GG1   Keynote 

Session
Rheology of Gels, Glasses and Jammed Systems

Title
A unified state diagram for the yielding transition of soft colloids

Presentation Date and Time
October 10, 2022 (Monday) 9:50

Track / Room
Track 3 / Sheraton 5

Authors (Click on name to view author profile)

1. Aime, Stefano (Molecular, Macromolecular Chemistry, and Materials, ESPCI)
2. Truzzolillo, Domenico (Laboratoire Charles Coulomb, CNRS-University of Montpellier)
3. Pine, David J. (Department of Physics, New York University)
4. Ramos, Laurence (Laboratoire Charles Coulomb, CNRS-University of Montpellier)
5. Cipelletti, Luca (Laboratoire Charles Coulomb, CNRS-University of Montpellier)

Author and Affiliation Lines (in printed abstract book)
Stefano Aime¹, Domenico Truzzolillo², David J. Pine³, Laurence Ramos² and Luca Cipelletti^2
1Molecular, Macromolecular Chemistry, and Materials, ESPCI, Paris, France; ²Laboratoire Charles Coulomb, CNRS-University of Montpellier, Montpellier, France; ³Department of Physics, New York University, New York, NY

Speaker / Presenter 
Aime, Stefano

Keywords
experimental methods; colloids; emulsions; glasses; jammed systems

Text of Abstract
Concentrated colloidal suspensions and emulsions are amorphous soft solids, widespread in technological and industrial applications and intensively studied as model systems in physics and material sciences. Soft solids are easily fluidized by applying a mechanical stress: this change in the macroscopic mechanical response is called the “yielding transition”, even though it usually appears as a smooth crossover whose location cannot be unambiguously defined. Yielding occurs with very similar macroscopic features in a diverse class of soft solids, irrespective of profound microstructural differences, which suggests the presence of an underlying general framework. However, despite consistent research efforts, no consensus on a unified description has emerged so far. Here, we investigate yielding in three classes of soft solids, with experiments probing simultaneously the microscopic dynamics and mechanical response under oscillatory shear. We find that at the microscopic level yielding consists in a well-defined transition between two distinct dynamical states, which surprisingly coexist at yielding. We propose a lattice model with dynamical coupling between neighboring sites that captures the generic features of our experiments, leading to a unified state diagram for yielding. Numerical simulations of this model show that disorder in the dynamical coupling plays a major role in the emergence of first-order-like vs second-order-like features in yielding, allowing for reconciling previous contrasting observations on the nature of the transition.