Arrest of fluid demixing by nanoparticles: a computer simulation study.

Area of Science:

• Soft Matter Physics
• Colloid Science
• Materials Science

Background:

• Binary solvent demixing with colloidal particles can form arrested structures.
• Previous simulations suggested bicontinuous interfacially jammed emulsion gels (bijels) form during symmetric quenches.
• Experimental studies confirmed bijel formation, even in asymmetric quenches.

Purpose of the Study:

• Investigate arrested structure formation in binary solvent demixing under asymmetric quenches.
• Compare results from asymmetric quenches to symmetric cases.
• Analyze the dynamics of particle ejection from interfaces in arrested structures.

Main Methods:

• Lattice Boltzmann simulations were employed to model the demixing process.
• Simulations focused on binary solvents with neutrally wetting colloidal particles.
• Analysis included post-arrest dynamics on timescales comparable to Brownian motion.

Main Results:

• A crossover from bijels to an arrested droplet phase was observed at strong volumetric asymmetry.
• New simulation results for asymmetric quenches were presented and compared to symmetric cases.
• The effective activation barrier for particle ejection from the fluid-fluid interface was found to be significantly lower (at least 2 orders of magnitude) than for isolated particles.

Conclusions:

• Asymmetric quenches lead to different arrested structures, including droplet phases.
• The interfacial jamming mechanism in bijels and arrested droplets is dynamic on intermediate timescales.
• Particle mobility at interfaces in arrested structures is higher than predicted by models for isolated particles.