Paper Number
SF1
Session
Self-assembly and Flow-induced Systems/Gels
Title
Role of dynamical heterogeneity in the rheology of colloidal gels
Presentation Date and Time
October 6, 2014 (Monday) 10:00
Track / Room
Track 6 / Washington C
Authors
- Hsiao, Lilian C. (University of Michigan, Chemical Engineering)
- Kang, Heekyoung (Seoul National University, School of Chemical and Biological Engineering)
- Ahn, Kyung Hyun (Seoul National University, School of Chemical and Biological Enigneering)
- Solomon, Michael J. (University of Michigan, Chemical Engineering)
Author and Affiliation Lines
Lilian C. Hsiao1, Heekyoung Kang2, Kyung Hyun Ahn2, and Michael J. Solomon1
1Chemical Engineering, University of Michigan, Ann Arbor, MI; 2School of Chemical and Biological Engineering, Seoul National University, Seoul, Republic of Korea
Speaker / Presenter
Solomon, Michael J.
Text of Abstract
Colloidal gels are known to exhibit complex structural and dynamical changes when sheared, particularly when the applied flow is strong enough to cause rupture. Here, we investigate the effect of shear-induced dynamical heterogeneity on the nonlinear elasticity of colloidal gels. These gels are comprised of fluorescent, sterically stabilized poly(methyl methacrylate) colloids that are suspended in refractive index and density matched solvents. Non-adsorbing polystyrene is added to induce gelation with weak, short-ranged attraction. We show that step strain deformations introduce a bimodal distribution in the van Hove self-correlation function, pointing to the existence of a fast and slow subpopulation of colloids within sheared gels. A simple modification of mode coupling theory that considers only the contribution of localized dynamics provides excellent agreement with the nonlinear elasticity of these gels across a broad range of deformations. These results experimentally support the concept that yielding causes the erosion of slow, hydrodynamically rigid clusters.