Paper Number
PO88 

Session
Poster Session

Title
Microstructural changes during yielding and flow of soft particle glasses

Presentation Date and Time
April 3, 2013 (Wednesday) 17:15

Track / Room
Poster Session / Jubileumzaal

Authors (Click on name to view author profile)

1. Mohan, Lavanya (The University of Texas at Austin, Department of Chemical Engineering)
2. Seth, Jyoti R. (The University of Texas at Austin, Department of Chemical Engineering)
3. Cloitre, Michel (ESPCI ParisTech, Matière Molle et Chimie)
4. Bonnecaze, Roger T. (University of Texas, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Lavanya Mohan¹, Jyoti R. Seth¹, Michel Cloitre², and Roger T. Bonnecaze^1
1Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, United States; ²Matière Molle et Chimie, ESPCI ParisTech, Paris, France

Speaker / Presenter 
Mohan, Lavanya

Text of Abstract
Soft particle glasses form a broad family of materials made of deformable particles, as diverse as microgels, emulsion droplets, star polymers and block copolymer micelles, which are jammed at large volume fractions where they are in contact and interact via soft elastic repulsions. They are yield stress fluids, that is, below a threshold stress they act like weak elastic solids and above it they begin to act like viscoelastic liquids. This combination of solid-like and liquid-like behavior of theirs is exploited to process high-performance coatings, ceramic pastes, textured food and personal care products. In order to use these materials more efficiently in above mentioned applications and to explore their use in other novel areas, it is important to connect their microstructural changes to their macroscopic properties. Here we use experiments and particle scale simulations of steady and oscillatory shear flow using a micromechanical model which includes elastic and viscous interactions [1] to establish this connection. At the particle or micro scale, the mean squared displacements of particles revealed that they remain trapped inside their cages at small amplitudes while at amplitudes much greater than the yield strain they undergo large scale rearrangements. The particle pair distribution functions were computed to look at the difference in microstructure in the different regimes. In the linear regime the pair distribution function was quite symmetric and comparable to the static case, but flow which introduces nonlinearities increased asymmetry of the pair distribution function and the maximum particle-particle compression. The elastic stress in the material was computed from its microstructure and it agreed well with the average value from macroscopic rheology. Finally these microstructural changes were compared to the macroscopic flow curves to establish the connection between them.

[1] J. R. Seth, L. Mohan, C. Locatelli-Champagne, M. Cloitre and R. T. Bonnecaze, Nat. Mater. 10 (2011), 838