Depletion-mediated potentials and phase behavior for micelles, macromolecules, nanoparticles, and hydrogel particles

Area of Science:

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

Background:

• Understanding depletion interactions is crucial for predicting phase behavior in colloidal systems.
• Existing models often struggle to capture the complex interplay between colloids and various depletants.

Purpose of the Study:

• To develop and validate a simple, accurate depletion potential for micrometer-sized colloids.
• To model colloid-surface potentials and quasi-2D phase behavior in the presence of diverse depletants.

Main Methods:

• Utilized Total Internal Reflection Microscopy (TIRM) to measure colloid-surface potentials.
• Employed Video Microscopy (VM) for observing quasi-2D phase behavior.
• Developed a modified Asakura-Oosawa (AO) depletion potential and performed Monte Carlo (MC) simulations.

Main Results:

• The modified AO potential accurately quantifies particle-wall potentials and interfacial crystallization.
• Effective depletant sizes, osmotic equations of state, and partition coefficients were incorporated.
• Partition coefficients served as the primary fitting parameter, with theoretical prediction also explored.

Conclusions:

• The developed depletion potential effectively models interactions and phase behavior in complex colloidal systems.
• This work provides a versatile tool for predicting colloidal assembly and interfacial phenomena.
• The model's accuracy was demonstrated across systems with charged micelles, nanoparticles, and macromolecules.