Paper Number
VP75
Session
Pre-recorded Flash Presentations (virtual)
Title
Influence of surface roughness on the yielding of thermo-reversible colloidal gels
Presentation Date and Time
All Week (Asynchronous) Any Time
Track / Room
Pre-recorded Presentation / Virtual
Authors
- Müller, Florence J. (ETH Zurich, Materials Departements)
- Vermant, Jan (ETH Zurich, Materials Departement)
Author and Affiliation Lines
Florence J. Müller and Jan Vermant
Materials Departement, ETH Zurich, Zurich 8093, Switzerland
Speaker / Presenter
Müller, Florence J.
Keywords
experimental methods; colloids; gels; rheology methods
Text of Abstract
The microstructural and solid-liquid transition of colloidal gels has been intensively researched using various characterization methods in the past [1,2]. In the present work we investigate the effect of surface topography on the yield stress and thixotropy. To this end, thermo-responsive octadecyl coated silica particles were synthesized in a controlled and reproducible manner using click-like chemistry to graft the stabilizer to particles with concave, convex and no surface features. The thermo-responsive nature allows to delete the influence of mechanical history, as gelation can be induced by decreasing the temperature inside the measurement cell. This model system is utilized to compare the initial yielding behavior of colloidal gels with primary particles of different surface topographies. Rheological measurements show that surface roughness delays the structural yielding due to interlocking of the particles, in addition to influencing the thixotropy as roughness counteracts flow induced cluster densification.\\ [1] Gopalakrishnan, V., and C. F. Zukoski. "Yielding behavior of thermo-reversible colloidal gels." Langmuir 23.15 (2007): 8187-8193. [2] Chan, Hubert K., and Ali Mohraz. "Two-step yielding and directional strain-induced strengthening in dilute colloidal gels." Physical Review E 85.4 (2012): 041403.