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Long-term aging behaviors in a model soft colloidal system.
Qi Li1, Xiaoguang Peng1, Gregory B McKenna1
1Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409, USA. greg.mckenna@ttu.edu.
Soft Matter
|January 26, 2017
Summary
Aging soft colloidal systems show distinct non-equilibrium behaviors. Their structural evolution and relaxation dynamics are decoupled, differing from molecular glasses and macroscopic rheology.
Area of Science:
- Soft Matter Physics
- Colloidal Science
- Glass Transition Physics
Background:
- Colloidal and molecular systems exhibit analogous behaviors near their glass transition points.
- Understanding aging dynamics in soft colloidal systems is crucial for material science applications.
Purpose of the Study:
- To investigate aging behaviors and equilibrium dynamics of a PS-PNIPAM/AA soft colloidal system after volume fraction up-jumps.
- To explore the transition from liquid to glassy states in colloidal dispersions under varying conditions.
Main Methods:
- Utilized diffusing wave spectroscopy (DWS), a light scattering technique, to study aging responses.
- Conducted long-term experiments (100,000 s) to capture both equilibrium and non-equilibrium dynamics.
- Investigated a wide range of effective volume fractions, extending deeper into the glassy domain.
Main Results:
- Equilibrium dynamics showed strong dependence on effective volume fraction and initial mass concentration.
- Observed deviations from Vogel-Fulcher-Tammann (VFT) predictions for α-relaxation time (τα) in the glassy domain.
- Demonstrated decoupling between structural evolution time and α-relaxation time in non-equilibrium aging.
Conclusions:
- The colloidal system displays unique non-equilibrium aging behavior distinct from molecular glasses.
- Super-Arrhenius signature in relaxation dynamics disappears above the glass transition volume fraction.
- Aging dynamics in soft colloidal systems are complex and differ from macroscopic rheological observations.
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