From single microgels to dense microgel monolayers - investigation by atomic force microscopy

Area of Science:

• Soft Matter Physics
• Materials Science
• Surface Chemistry

Background:

• Microgels possess unique properties driving interest in interfacial applications.
• Understanding microgel behavior in confined environments is crucial for advanced material design.

Purpose of the Study:

• To investigate the internal structure and phase behavior of microgels in monolayers at solid-liquid interfaces.
• To analyze the impact of varying surface pressures on microgel structural responses.

Main Methods:

• Utilized Atomic Force Microscopy (AFM) to probe microgel monolayers.
• Deposited microgel monolayers at different surface pressures to study compression effects.
• Recorded force-distance curves to analyze interactions and structural changes.

Main Results:

• Microgel confinement in dense monolayers increases internal stiffness and polymer density from the third compression regime.
• Compression at the solid-liquid interface induces attractive interactions between microgels and the AFM tip.
• Observed jumps-to-contact in force-distance curves indicate a structural transition within the microgel monolayer.

Conclusions:

• Microgel monolayers exhibit significant structural changes under compression at solid-liquid interfaces.
• Compression leads to increased polymer density and emergent attractive forces, suggesting altered inter-microgel interactions.
• AFM is a powerful tool for revealing microgel structural transitions and interfacial behaviors.