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Communication: Is directed percolation in colloid-polymer mixtures linked to dynamic arrest?
David Richard1, C Patrick Royall2, Thomas Speck1
1Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7-9, 55128 Mainz, Germany.
The Journal of Chemical Physics
|July 2, 2018
Summary
Computer simulations reveal that competing repulsions in colloid-polymer mixtures do not alter the fundamental process of dynamic arrest (gelation). Arrest occurs near the spinodal, not at the percolation transition.
Area of Science:
- Soft matter physics
- Colloid science
- Polymer physics
Background:
- Colloid-polymer mixtures can form arrested gels, characterized by rigid networks of colloidal particles.
- Dynamic arrest, or gelation, is crucial for understanding material properties.
- Previous work suggested a link between directed percolation (DP) and the onset of dynamic arrest.
Purpose of the Study:
- To investigate dynamic arrest in colloid-polymer mixtures with competing interactions.
- To evaluate the influence of repulsions on the binodal and percolation transitions.
- To clarify the relationship between percolation and dynamic arrest.
Main Methods:
- Utilizing computer simulations to model colloid-polymer mixtures.
- Analyzing schematic models with short-ranged attractions and long-ranged repulsions.
- Evaluating gas-liquid binodal and percolation transitions for various screening lengths.
Main Results:
- Directed percolation shifts the percolation line to higher densities.
- The suspension remains ergodic even beyond the DP line.
- Dynamic arrest is observed only near the spinodal, not at the percolation threshold.
Conclusions:
- Competing repulsions do not qualitatively change the scenario of non-equilibrium gelation.
- Dynamic arrest is primarily governed by the spinodal, independent of percolation.
- Structural differences in the percolating network exist despite the unchanged gelation scenario.
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