Paper Number
GG1 

Session
Arrested Systems: Gels and Glasses

Title
Time–connectivity superposition and the gel/glass duality of weak colloidal gels

Presentation Date and Time
October 11, 2021 (Monday) 9:50

Track / Room
Track 6 / Ballroom 1

Authors (Click on name to view author profile)

  1. Keshavarz, Bavand (Massachusetts Institute of Technology)
  2. Gomes Rodrigues, Donatien (CEA Marcoule)
  3. Champenois, Jean-Baptiste (CEA Marcoule)
  4. Frith, Matt (Argonne National Laboratory, Advanced Photon Source)
  5. Ilavsky, Jan (Argonne National Laboratory, Advanced Photon Source)
  6. Geri, Michela (Massachusetts Institute of Technology)
  7. Divoux, Thibaut (ENS Lyon, CNRS)
  8. McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
  9. Poulesquen, Arnaud (CEA Marcoule)

Author and Affiliation Lines (in printed abstract book)
Bavand Keshavarz1, Donatien Gomes Rodrigues2, Jean-Baptiste Champenois2, Matt Frith3, Jan Ilavsky3, Michela Geri1, Thibaut Divoux4, Gareth H. McKinley1 and Arnaud Poulesquen2
1Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA; 2CEA Marcoule, Bagnols-sur-Cèze, France; 3Advanced Photon Source, Argonne National Laboratory, Argonne, IL; 4CNRS, ENS Lyon, Lyon, France

Speaker / Presenter 
Keshavarz, Bavand

Keywords
gels; glasses

Text of Abstract
Colloidal gels result from the aggregation of Brownian particles suspended in a solvent. Gelation is induced by attractive interactions between individual particles that drive the formation of clusters, which in turn aggregate to form a space-spanning structure. We study this process in aluminosilicate colloidal gels through time-resolved structural and mechanical spectroscopy. Using the time–connectivity superposition principle a series of rapidly acquired linear viscoelastic spectra, measured throughout the gelation process by applying an exponential chirp protocol, are rescaled onto a universal master curve that spans over eight orders of magnitude in reduced frequency. This analysis reveals that the underlying relaxation time spectrum of the colloidal gel is symmetric in time with power-law tails characterized by a single exponent that is set at the gel point. The microstructural mechanical network has a dual character; at short length scales and fast times it appears glassy, whereas at longer times and larger scales it is gel-like. These results can be captured by a simple three-parameter constitutive model and demonstrate that the microstructure of a mature colloidal gel bears the residual skeleton of the original sample-spanning network that is created at the gel point. Our conclusions are confirmed by applying the same technique to another well-known colloidal gel system composed of attractive silica nanoparticles. The results illustrate the power of the time–connectivity superposition principle for this class of soft glassy materials and provide a compact description for the dichotomous viscoelastic nature of weak colloidal gels.