Charge affinity and solvent effects in numerical simulations of ionic microgels.

Area of Science:

• Soft Matter Physics
• Polymer Science
• Colloid Chemistry

Background:

• Ionic microgels are thermo-responsive polymeric colloids with added charged groups.
• Accurate modeling of single particles is crucial for predicting microgel suspension behavior.
• Existing models require refinement for ionic groups within the polymer network.

Purpose of the Study:

• To numerically advance a model for charged co-polymerized microgels.
• To improve the treatment of ionic groups in the polymer network.
• To investigate the thermoresponsive swelling behavior and structure of ionic microgels.

Main Methods:

• Developed an improved coarse-graining strategy for ionic microgels.
• Enhanced the treatment of ionic groups within the polymer network.
• Explicitly included solvent interactions in the model.

Main Results:

• Highly charged microgels do not fully collapse at lower temperatures when ionic groups are hydrophilic.
• The model accurately predicts swelling behavior and structure, showing favorable comparison to experimental data.
• A mapping between solvophobic potentials and monomer-solvent interactions was established and validated for all charge fractions.

Conclusions:

• The refined model provides accurate predictions for single ionic microgel particle properties and swelling.
• This work enables direct comparison with experimental results for ionic microgels.
• Facilitates future studies on charged soft particles, including their behavior at liquid-liquid interfaces.