A Thermodynamic Model for Contact Angle Hysteresis

Area of Science:

• Surface Science
• Physical Chemistry
• Materials Science

Background:

• Contact angle hysteresis is a common phenomenon in wetting processes.
• Its thermodynamic origins are not fully understood, potentially involving surface imperfections or irreversible interactions.

Purpose of the Study:

• To derive thermodynamic expressions for the free energy of contact angle hysteresis.
• To model wetting as an adsorption-desorption process and quantify associated free energies.

Main Methods:

• Development of thermodynamic expressions for free energy.
• Modeling wetting as an adsorption-desorption process.
• Analysis of experimental data from various polymer and surfactant surfaces using different liquids.

Main Results:

• The model demonstrates that substantial free energies can be associated with near-zero contact angles.
• Experimental data yielded consistent free energy values across different liquids for each surface.
• Nonpolar polymer surfaces showed free energies consistent with van der Waals interactions.
• Polar polymer surfaces exhibited higher free energies, suggesting stronger interactions and interface restructuring.

Conclusions:

• The derived thermodynamic model provides a framework for understanding contact angle hysteresis.
• The free energy of hysteresis is influenced by surface polarity and intermolecular interactions.
• This work quantifies hysteresis-related free energies, offering insights into wetting phenomena on diverse materials.