Surface observation of solvent-impregnated Nafion membrane with atomic force microscopy

Area of Science:

• Materials Science
• Polymer Science
• Surface Science

Background:

• Nafion 117 is a widely used ion-exchange membrane in various electrochemical applications.
• Understanding its surface morphology is crucial for optimizing performance.
• Solvent interactions can significantly alter polymer membrane structure.

Purpose of the Study:

• To investigate the surface morphology modification of Nafion 117 membranes.
• To study the effects of water and methanol on Nafion topography and structure.
• To correlate surface changes with solvent-induced swelling phenomena.

Main Methods:

• Atomic Force Microscopy (AFM) was employed to analyze surface morphology.
• Contact and tapping AFM modes were utilized to probe surface features.
• AFM phase imaging was used to distinguish domain structures.

Main Results:

• Nafion 117 topography significantly changes upon water absorption.
• Samples stored in methanol exhibit a flatter surface topography.
• Surface modification is attributed to solvent-induced expansion and swelling.
• Tapping-mode phase images revealed distinguishable ionic and cluster domains in both water- and methanol-impregnated samples.

Conclusions:

• The interaction of Nafion 117 with water and methanol leads to distinct surface morphological changes.
• Solvent-induced swelling is a key factor in the observed surface modifications.
• AFM is effective in visualizing the microstructural changes and domain features on Nafion surfaces.