Temperature-sensitive soft microgels at interfaces: air-water versus oil-water

Area of Science:

• Colloid and Surface Science
• Materials Science
• Polymer Science

Background:

• Smart emulsions and foams require controllable stability using external stimuli.
• Microgels are promising smart stabilizers, acting as nano- and micro-sized polymer networks.
• Previous research focused on stimuli-responsive microgel behavior, neglecting the top-phase influence.

Purpose of the Study:

• To investigate the impact of the top-phase on microgel properties at interfaces.
• To understand how interfacial tension affects microgel dimensions and elasticity.
• To determine if microgel 2D phase behavior is altered by interfacial tension.

Main Methods:

• Deposition of poly(N-isopropylacrylamide) (pNIPAM) microgels at air-water and decane-water interfaces.
• Measurement of microgel dimensions and area occupied at different interfaces.
• Correlation of microgel area with surface tension to estimate elastic modulus; comparison with nanoindentation.

Main Results:

• Microgel in-plane size increases with rising interfacial tension.
• The fraction of microgels in the aqueous phase remains unaffected by interfacial tension.
• Estimated elastic modulus from interfacial measurements is higher than that from nanoindentation.

Conclusions:

• The top-phase significantly influences microgel dimensions at interfaces.
• Microgel 2D phase behavior is robust and unaltered despite changes in interfacial tension.
• Microgels offer tunable interfacial properties for advanced smart material applications.