Monitoring Chemical Cross-Linking Reactions at Liquid Interfaces with Dilational Rheometry and General Stress...

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Chemical cross-linking reactions at interfaces form thin membranes, crucial for many scientific challenges.
• Interfacial rheology offers sensitive monitoring of mechanical properties, but classical methods struggle with solid-like interfaces.
• Oscillating drop techniques face limitations due to rapid nonlinear responses in developing interfacial membranes.

Purpose of the Study:

• To introduce and validate General Stress Decomposition (GSD) for analyzing mechanical responses of interfacial membranes.
• To disentangle linear viscoelastic and nonlinear components of membrane mechanics during development.
• To gain deeper insights into membrane growth kinetics and internal stresses.

Main Methods:

• Utilizing sensitive pressure measurements from an oscillating, spherical drop.
• Applying General Stress Decomposition (GSD) to analyze interfacial mechanical responses.
• Employing a model system of a cross-linking reaction at a PEG-silicone interface.

Main Results:

• GSD successfully separates linear viscoelastic and nonlinear contributions to membrane mechanics.
• The study reveals the impact of formulation parameters on membrane growth kinetics.
• Internal mechanical stresses in forming membranes were identified, clarifying previous misinterpretations.

Conclusions:

• GSD is an effective technique for detailed analysis of interfacial membrane mechanics.
• The method provides superior insight into membrane formation compared to classical rheology.
• Accurate characterization of internal stresses is crucial for understanding interfacial membrane behavior.