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Torsional stiffness determines aggregate structure in sheared colloidal rod suspensions.
Justin T Stimatze1, David A Egolf1, Jeffrey S Urbach1
1Department of Physics and Institute for Soft Matter Synthesis and Metrology, Georgetown University, Washington, DC, USA. urbachj@georgetown.edu.
Soft Matter
|October 8, 2016
Summary
Simulations show that attractive forces and shear alignment in rigid rod suspensions form aligned bundles. Torsional stiffness in contacts leads to disordered aggregates, influencing alignment and viscosity.
Area of Science:
- Soft Matter Physics
- Computational Fluid Dynamics
Background:
- Understanding particle interactions is crucial for predicting suspension behavior.
- Shear forces and inter-particle attractions significantly influence microstructure in colloidal systems.
Purpose of the Study:
- To investigate the self-assembly and structural evolution of sheared rigid rod suspensions.
- To explore the impact of inter-particle attractions and torsional stiffness on aggregate formation.
Main Methods:
- Dissipative particle dynamics (DPD) simulations were employed for coarse-grained modeling.
- Simulations analyzed suspensions of rigid rods under shear flow with varying attractive interactions and contact stiffness.
Main Results:
- Attractive interactions and shear-induced alignment generically produce aggregates of aligned bundles when rod contacts can rotate.
- Introducing torsional stiffness to contacts results in disordered aggregates, mimicking experimental observations for high aspect ratio particles.
- Aggregate alignment degree is sensitive to torsional stiffness, while aggregate stability and viscosity depend on attractive forces versus shear stress.
Conclusions:
- Torsional stiffness at inter-particle contacts is a key factor in determining aggregate structure in sheared rod suspensions.
- The interplay between attractive forces and shear stress governs aggregate stability and rheological properties.
- Simulation results provide insights into the complex behavior of concentrated colloidal suspensions.
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