Paper Number
SC10 

Session
Suspensions, Colloids and Granular Systems

Title
Structure, elasticity, and non-equilibrium state diagram of depletion gels

Presentation Date and Time
October 9, 2017 (Monday) 3:45

Track / Room
Track 3 / Crystal C

Authors (Click on name to view author profile)

1. Furst, Eric M. (Univ. of Delaware, Dept. of Chemical & Biomolecular Engineering)
2. Whitaker, Kathryn A. (Univesrity of Delaware, Department of Chemical and Biomolecular Engineering)
3. Hsiao, Lilian C. (North Carolina State University, Department of Chemical and Biomolecular Engineering)
4. Solomon, Michael J. (University of Michigan, Ann Arbor, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Eric M. Furst¹, Kathryn A. Whitaker¹, Lilian C. Hsiao², and Michael J. Solomon^3
1Dept. of Chemical & Biomolecular Engineering, Univ. of Delaware, Newark, MD; ²Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27606; ³Chemical Engineering, University of Michigan, Ann Arbor, Ann Arbor, MI 48105

Speaker / Presenter 
Furst, Eric M.

Text of Abstract
We use a recent model depletion gel that enables the rheology, structure, and particle interactions to be measured in concert [1]. As the attractive strength between particles increases, the gel elastic modulus increases, but that this change cannot be accounted for by the immediate increase in bond stiffness between particles and clusters alone derived from the depletion interaction energy. The modulus is, however, consistent with an increasing number of cluster-cluster contacts. Based on the cluster model of gel rheology, two principal length scales emerge: at the particle level, the internal cluster structure becomes less dense with increasing attractive strength, and extends from the attractive glass line of colloids with short range attraction into the lower density gel region, similar to recent studies of protein gels [2], but in contrast to prior studies of suspensions that rely solely on imaging the microstructure [3]. However, the size of the clusters, the length scale over which stress is transmitted during elastic deformation, does not depend on the magnitude of the attractive strength; its origin remains an open question. These results confirm that there is an intimate connection between the gelation of colloids with short-range attraction and phase separation. Remarkably, the cluster gel model gives consistent results for depletion gels that span a range of length scales and chemistries, but otherwise capture the same relative range of attraction and interaction strengths [4].

[1] L. C. Hsiao, M. J. Solomon, K. A. Whitaker, and E. M. Furst, J. Rheol. 58, 1485–1504 (2014).
[2] F. Cardinaux, T. Gibaud, A. Stradner, and P. Schurtenberger, Phys. Rev. Lett. 99, 118301 (2007).
[3] P. J. Lu, E. Zaccarelli, F. Ciulla, A. B. Schofield, F. Sciortino, and D. A. Weitz, Nature 453, 499–504 (2008).
[4] S. Ramakrishnan, Y.-L. Chen, K. S. Schweizer, and C. F. Zukoski, Phys. Rev. E 70, 040401(R) (2004).