Yielding behavior of thermo-reversible colloidal gels.
V Gopalakrishnan1, C F Zukoski
1Department of Chemical and Biomolecular Engineering, University of Illinois, Urbana, IL 61801, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 15, 2007
Summary
We explored how stress causes flow in thermo-reversible gels. A barrier-hopping theory accurately predicted the yield stress, showing how particle interactions and external forces affect gel structure and mechanical properties.
Area of Science:
- Colloid and Surface Science
- Rheology
- Soft Matter Physics
Background:
- Gelled suspensions exhibit structural breakdown under stress, leading to flow.
- Thermo-reversible gels are widely studied systems displaying a liquid-to-gel transition dependent on temperature and volume fraction.
Purpose of the Study:
- To investigate the onset of flow in thermo-reversible gels by examining nonlinear behavior in elastic moduli.
- To test the predictive power of activated barrier-hopping theory for structurally arrested systems under stress.
Main Methods:
- Utilized a system of octadecyl-coated silica particles in decalin.
- Measured perturbative yield stress as a function of volume fraction and temperature.
- Employed activated barrier-hopping theory with a Yukawa potential and static structure factor to model elastic modulus evolution.
Main Results:
- Perturbative yield stress increased monotonically with volume fraction and decreasing temperature.
- The activated barrier-hopping theory quantitatively captured the experimental yield stresses across all conditions.
- The theory successfully predicted how elastic modulus changes with applied stress.
Conclusions:
- Activated barrier-hopping theory accurately describes the mechanical response of gels to external stress.
- The theory captures particle localization and its modulation by applied forces in structurally arrested systems.
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