An Effective Volume Fraction Controls Both Dynamics and Thermodynamics in Vesicle Suspensions with Tunable...

Area of Science:

• Colloid and Surface Science
• Soft Matter Physics
• Computational Chemistry

Background:

• Surfactant vesicle suspensions are vital colloidal systems with applications in industry and biomedicine.
• Electrostatic interactions between charged vesicles and electrolytes significantly influence system stability and dynamics.

Purpose of the Study:

• To investigate the impact of volume fraction and electrolyte concentration on the microscopic structure and dynamics of charged vesicle suspensions.
• To develop a predictive model for understanding vesicle behavior in different solution conditions.

Main Methods:

• Brownian dynamics simulations were performed for charged spherical vesicles in sodium-bromide solutions.
• Interaction parameters were derived from experimental data for realistic simulations.

Main Results:

• A colloidal state diagram was established, revealing shifts in dilute-to-dense and fluid-to-arrested transitions with decreasing electrolyte concentration.
• Electrolyte concentration and vesicle interactions were found to influence inter-vesicle distances and radial distribution.
• An effective volume fraction was defined, collapsing dynamic and thermodynamic indicators onto salt-independent master curves, simplifying the state diagram to one dimension.

Conclusions:

• The study provides a comprehensive understanding of charged vesicle behavior influenced by electrostatic interactions and electrolyte concentration.
• The findings enable better prediction and design of novel formulations containing charged vesicles.
• The development of a one-dimensional state diagram offers a simplified yet powerful tool for characterizing these colloidal systems.