Softness matters: effects of compression on the behavior of adsorbed microgels at interfaces.

Deformable colloids and macromolecules adsorb at interfaces as they decrease the interfacial energy between the two media. The deformability, or softness, of these particles plays a pivotal role in the properties of the interface. In this study, we employ a comprehensive approach, combining neutron reflectometry with molecular dynamics simulations, to thoroughly examine the profound influence of softness on the structure of microgel Langmuir monolayers under compression.

Interfacial Fluid Rheology of Soft Particles.

In situ interfacial rheology and numerical simulations are used to investigate microgel monolayers in a wide range of packing fractions, ζ_{2D}. The heterogeneous particle compressibility determines two flow regimes characterized by distinct master curves. To mimic the microgel architecture and reproduce experiments, an interaction potential combining a soft shoulder with the Hertzian model is introduced.

Self-Healing of Charged Microgels in Neutral and Charged Environments.

The softness of microgels depends on many aspects, such as particle characteristic lengths, sample concentration, chemical composition of the sample, and elastic moduli of the particle. Here, the response to crowding of ionic microgels is studied. Charged and uncharged ionic microgels are studied in concentrated suspensions of both neutral and ionic microgels with the same swollen size.

In-situ study of the impact of temperature and architecture on the interfacial structure of microgels.

The structural characterization of microgels at interfaces is fundamental to understand both their 2D phase behavior and their role as stabilizers that enable emulsions to be broken on demand. However, this characterization is usually limited by available experimental techniques, which do not allow a direct investigation at interfaces. To overcome this difficulty, here we employ neutron reflectometry, which allows us to probe the structure and responsiveness of the microgels in-situ at the air-water interface.

Anisotropic Microgels Show Their Soft Side.

Anisotropic, submicrometer-sized particles are versatile systems providing interesting features in creating ordering in two-dimensional systems. Combining hard ellipsoids with a soft shell further enhances the opportunities to trigger and control order and alignment. In this work, we report rich 2D phase behavior and show how softness affects the ordering of anisotropic particles at fluid oil-water interfaces.

Influence of Charges on the Behavior of Polyelectrolyte Microgels Confined to Oil-Water Interfaces.

The role of electrostatics on the interfacial properties of polyelectrolyte microgels has been discussed controversially in the literature. It is not yet clear if, or how, Coulomb interactions affect their behavior under interfacial confinement. In this work, we combine compression isotherms, atomic force microscopy imaging, and computer simulations to further investigate the behavior of pH-responsive microgels at oil-water interfaces.

How gold nanoparticles can be used to probe the structural changes of a pH-responsive hydrogel.

Gold nanoparticles (GNPs) have UV-visible absorption spectra that are highly sensitive to their local environment due to their surface plasmon resonance (SPR). Furthermore, GNPs are able to quench the fluorescence of suitable dyes depending on the GNP-dye separation. Both of these features have led to the use of GNPs as spectroscopic rulers.