Tuning the Interactions in Multiresponsive Complex Coacervate-Based Underwater Adhesives

Area of Science:

• Materials Science
• Polymer Chemistry
• Surface Chemistry

Background:

• Underwater adhesives are crucial for various applications but often rely on reactive chemistries.
• Complex coacervates offer tunable properties through non-covalent interactions.
• Thermoresponsive polymers like poly(N-isopropylacrylamide) (PNIPAM) can introduce dynamic responses to materials.

Purpose of the Study:

• To systematically investigate a multiresponsive complex coacervate-based underwater adhesive.
• To understand the influence of ionic strength and PNIPAM content on adhesive properties.
• To optimize the formulation for enhanced underwater adhesion performance.

Main Methods:

• Fabrication of complex coacervates incorporating polyelectrolyte domains and PNIPAM.
• Systematic variation of ionic strength (NaCl concentration) and PNIPAM content.
• Characterization of thermal, rheological, and adhesive properties under varying conditions.

Main Results:

• The developed adhesive transitions from liquid to solid via non-covalent interactions (electrostatic and hydrophobic).
• Mechanical properties are dependent on preparation conditions and environment, forming a kinetically trapped morphology.
• Optimal adhesion (6.5 J/m²) achieved at 0.75 M NaCl and ~30% mol/mol PNIPAM content.
• High ionic strength facilitated injectability, while PNIPAM domains provided energy dissipation.

Conclusions:

• The complex coacervate system demonstrates tunable underwater adhesive properties.
• Formulation optimization through ionic strength and PNIPAM content is key for performance.
• Non-covalent interactions provide a robust and adaptable mechanism for underwater adhesion.