Formation of a transient amorphous solid in low density aqueous charged sphere suspensions

Area of Science:

• Materials Science
• Soft Matter Physics
• Physical Chemistry

Background:

• Colloidal glasses are well-studied, but experimental charged sphere glasses at low densities have remained elusive due to competing crystallization.
• Previous research focused on hard spheres, ellipsoids, and platelets, advancing general glass transition understanding.

Purpose of the Study:

• To report the first experimental observation of charged sphere glasses at low densities.
• To characterize the properties and transformation of these novel colloidal glasses.

Main Methods:

• Optical experiments to observe short-range order and shear rigidity.
• Dynamic light scattering to probe relaxation processes and dynamic heterogeneity.
• Comparison with theoretical predictions and simulations of charged sphere suspensions.

Main Results:

• Formation of a transient amorphous solid from charged polymer spheres at low volume fractions (0.0002-0.01).
• Observed short-range order and enhanced shear rigidity compared to the stable body-centered cubic crystalline solid.
• Transformation of the amorphous solid into the crystalline structure on a timescale of hours to days.
• Preliminary dynamic light scattering data suggest a second slow relaxation process, indicating potential dynamic heterogeneity.

Conclusions:

• The study presents the first experimental evidence of low-density charged sphere glasses.
• The findings provide insights into the formation and transformation mechanisms of colloidal glasses.
• This work bridges the gap between theoretical predictions and experimental realization in charged colloidal systems.