Ionic group-dependent structure of complex coacervate hydrogels formed by ABA triblock copolymers

Area of Science:

• Polymer Science
• Materials Science
• Soft Matter Physics

Background:

• Complex coacervate core hydrogels (C3Gs) are formed from oppositely charged polymers.
• Understanding their nanostructure is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the nanostructure of C3Gs with varying cationic charged groups (ammonium and guanidinium).
• To determine how guanidinium fraction and salt concentration affect C3G properties.
• To explore the control over salt-responsiveness in C3Gs.

Main Methods:

• Preparation of C3Gs using ABA triblock copolymers with functionalized end-blocks.
• Stoichiometric mixing of oppositely charged polymers in aqueous solutions.
• Small-angle X-ray/neutron scattering (SAX/NS) for structural analysis.

Main Results:

• Increased guanidinium fraction enhances polymer volume fraction, interfacial tension, and salt resistance in C3G cores.
• Hydrophobicity and non-electrostatic associations contribute to increased salt resistance.
• Interfacial tension follows a specific salt dependence: γcore ∼ (1 - cs/c*)3/2.

Conclusions:

• Varying ionic groups in C3Gs allows for precise control over their nanostructure and salt-responsiveness.
• This provides a powerful strategy for developing tunable stimuli-responsive materials.
• Findings offer insights into designing hydrogels with tailored properties for specific applications.