Low-Rate Dynamic Contact Angles on Poly(methyl methacrylate) and the Determination of Solid Surface Tensions

Area of Science:

• Materials Science
• Physical Chemistry
• Polymer Science

Background:

• Understanding liquid-solid interactions is crucial for material applications.
• Contact angle measurements provide insights into surface properties and interfacial phenomena.
• Poly(methyl methacrylate) (PMMA) is a widely used polymer with diverse applications.

Purpose of the Study:

• To investigate the dynamic contact angles of various liquids on PMMA.
• To explore the relationship between liquid-vapor surface tension and contact angles on PMMA.
• To determine the solid-vapor surface tension of PMMA using experimental data.

Main Methods:

• Automated axisymmetric drop shape analysis-profile (ADSA-P) was employed to measure low-rate dynamic contact angles.
• Nine different liquids, including polar and nonpolar, were tested on a PMMA surface.
• Contact angle data were analyzed in conjunction with liquid-vapor surface tension values.

Main Results:

• Two liquids caused polymer dissolution upon contact.
• For the remaining seven liquids, the product of liquid-vapor surface tension and the cosine of the contact angle correlated smoothly with liquid-vapor surface tension.
• This relationship was consistent across different methacrylate polymers, indicating predictable interfacial behavior.
• The solid-vapor surface tension of PMMA was determined to be 38.5 mJ/m² (±0.5 mJ/m²).

Conclusions:

• Young's equation governs the relationship between solid-vapor, liquid-vapor, and solid-liquid interfacial tensions.
• The observed contact angle patterns are consistent with those found on other polymer surfaces.
• The study provides a reliable method for characterizing polymer surface properties and interfacial tensions.