Paper Number
GG5 

Session
Rheology of Gels, Glasses and Jammed Systems

Title
Transient yielding of attractive soft particle glasses

Presentation Date and Time
October 10, 2022 (Monday) 11:10

Track / Room
Track 3 / Sheraton 5

Authors (Click on name to view author profile)

  1. Di Dio, Bruno F. (ESPCI Paris - PSL, Molecular, Macromolecular Chemistry and Materials)
  2. Khabaz, Fardin (The University of Akron, School of Polymer Science and Polymer Engineering)
  3. Bonnecaze, Roger T. (University of Texas at Austin, Department of Chemical Engineering)
  4. Cloitre, Michel (ESPCI Paris - PSL, Molecular, Macromolecular Chemistry and Materials)

Author and Affiliation Lines (in printed abstract book)
Bruno F. Di Dio1, Fardin Khabaz2, Roger T. Bonnecaze3 and Michel Cloitre1
1Molecular, Macromolecular Chemistry and Materials, ESPCI Paris - PSL, Paris, France; 2School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH; 3Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712

Speaker / Presenter 
Di Dio, Bruno F.

Keywords
experimental methods; colloids; emulsions; foams; gels; glasses; jammed systems; polymer melts; polymer solutions; surfactants; suspensions

Text of Abstract
Soft particle glasses are jammed suspensions of deformable particles dispersed in a suspending fluid. They respond elastically to small deformations but flow when subjected to large solicitations. The way SPGs switch from solid to liquid behavior is characterized by stress overshoots followed by stress relaxation towards steady state. On a fundamental level, the transient response reveals the microstructural mechanisms at the origin of yielding and flow. Recently we have studied SPGs with purely repulsive interactions, using a combination of particle dynamic simulations and experiments. The stress overshoots scaled by the dynamic yield stress follow universal variations when the shear rate is made non-dimensional using the viscosity of the solvent and the low-frequency modulus [1].

Here we investigate a class of SPGs where the particles experience short range adhesive forces. These attractive SPGs are made of microgels functionalized with alkyl groups which stick together when particles are in contact. Associative SPGs behave like repulsive glasses at low frequency, where interparticle associations are fully relaxed, and gels at high frequency where particles are trapped in sticky cages [2]. We analyze the transient yielding of these materials as a function of the applied shear rate, systematically varying the microgel concentration and the suspending fluid viscosity. At low shear rates, both the amplitude and the position of the stress overshoots are increased with respect to their values for repulsive SPGs due to the additional friction associated with short range interactions. At high shear rates, there is an interplay between yielding and the development of shear bands. Our findings open new perspectives to develop soft materials with tailored properties in a rational way.

[1] F. Khabaz, B.F. Di Dio, M. Cloitre, R.T Bonnecaze, J. Rheol. 65, 241 (2021); B.F. Di Dio, F. Khabaz, R.T. Bonnecaze, M. Cloitre, J.Rheol. accepted (2022)
[2] A. Shahmohammadi, R.T Bonnecaze, J. Rheol. 65, 463 (2021).