Structure and Rheology of Microgel Monolayers at the Water/Oil Interface

Abstract

We investigate the rheological property of microgel monolayers at the water/oil interface using passive and active microrheological methods. At low surface coverage, the microgels at the water/oil interface have a tendency to form aggregated structures (networks) with dominating elasticity. At high surface coverage the microgels form densely packed monolayers. Using microsized magnetic particles as the local rheological probes in the dense microgel monolayers, we perform in situ study of their rheological properties and structures. We observe four regimes where the elasticity of the microgel monolayer has different dependence on the microgel concentration at the interface. The rheological properties of the microgel monolayers are not only dependent on the concentration but also strongly correlated with the intermicrogel distance and spacial arrangement of the microgels at the interface. Our results also show that the microgel monolayers act similar to soft glassy materials.