Interfacial rheology of model water-air microgels laden interfaces: effect of cross-linking

Hypothesis The mechanical properties of model air/water interfaces covered by poly(Nisopropylacrylamide) microgels depend on the microgels deformability or in other words on the amount of cross-linker added during synthesis.Experiments The study is carried out by measuring the apparent dilational, the compression and the shear moduli using three complementary methods: 1) the pendant drop method with perturbative areas, 2) the Langmuir trough compression, and 3) shear rheology using a double wall ring cell mounted onto a Langmuir through.Findings In the range of surface coverages studied, the interfaces exhibit a solid-like behavior and elasticity goes through a maximum as a function of the surface pressure. This is observable whatever the investigation method. This maximum elasticity depends on the microgel deformability: the softer the microgels the higher the value of the moduli. The mechanical behavior of model interfaces is discussed, taking into account the core-shell structure of the particles and their packing at the interface