Theory and quantitative assessment of pH-responsive polyzwitterion-polyelectrolyte complexation

Area of Science:

• Polymer Chemistry
• Materials Science
• Physical Chemistry

Background:

• Polymer complex coacervates are formed by oppositely charged polymers.
• Polyzwitterions, with both positive and negative charges, exhibit complex pH-dependent behavior.
• Understanding polyzwitterion-polyelectrolyte interactions is crucial for designing novel materials.

Purpose of the Study:

• To introduce a theoretical framework for describing pH-sensitive phase behavior in polyzwitterion-polyelectrolyte complex coacervates.
• To capture recent experimental observations using this theoretical model.
• To explore the influence of various polymer properties on complexation.

Main Methods:

• Describing polyzwitterions by monomer states (dipolar, quasi-cationic, quasi-anionic, neutralized).
• Investigating effects of pKa, salt condensation, polymerization degree, hydrophobicity, and dipole lengths.
• Analyzing complexation windows across various stoichiometric ratios.

Main Results:

• The framework reasonably captures experimental observations of pH-sensitive phase behavior.
• Properties determining the polyzwitterion's net charge have the most significant impact on complexation pH range.
• Hydrophobicity and dipole lengths also influence the complexation window.

Conclusions:

• The theoretical framework provides a valuable tool for understanding polyzwitterion-polyelectrolyte complex coacervates.
• Molecular design guidance is offered for tuning complexation properties.
• Future research opportunities in polyzwitterion complex coacervates are highlighted.