Exploring the 3D Conformation of Hard‐Core Soft‐Shell Particles Adsorbed at a Fluid Interface

Abstract

The encapsulation of a rigid core within a soft polymeric shell allows obtaining composite colloidal particles that retain functional properties, e.g., optical or mechanical. At the same time, it favors their adsorption at fluid interfaces with a tunable interaction potential to realize tailored two‐dimensional (2D) materials. Although they have already been employed for 2D assembly, the conformation of single particles, which is essential to define the monolayer properties, has been largely inferred via indirect or ex situ techniques. Here, by means of in situ atomic force microscopy experiments, the authors uncover the interfacial morphology of hard‐core soft‐shell microgels, integrating the data with numerical simulations to elucidate the role of the core properties, of the shell thicknesses, and that of the grafting density. They identify that the hard core can influence the conformation of the polymer shells. In particular, for the case of small shell thickness, low grafting density, or poor core affinity for water, the core protrudes more into the organic phase, and the authors observe a decrease in‐plane stretching of the network at the interface. By rationalizing their general wetting behavior, such composite particles can be designed to exhibit specific inter‐particle interactions of importance both for the stabilization of interfaces and for the fabrication of 2D materials with tailored functional properties.

Relationship between π–A isotherms and single microgel/microgel array structures revealed via the direct visualization of microgels at the air/water interface

“…To date, the visualization of the 2D hexagonal structure of compressed and deformed microgels at fluid interfaces has been conducted by using the interface of sessile dispersion droplets, 49,53,54 different from the three-dimensionally compressed microgels in colloidal crystals. 55,56 However, the results of such analyses have been limited to observation conditions where the compression could not be controlled, that is, the structural changes of the individual microgels/microgel arrays packed at the interface during compression has not been well understood.…”

Nanocrystal Assemblies: Current Advances and Open Problems

“…Microstructural analysis of monolayers prepared via fluid interface-assisted assembly typically relies on microscopy (atomic force and electron microscopy) and scattering (X-ray and light scattering). , The application of such techniques assumes the microstructure is conserved during transfer to a solid interface and subsequent drying, which might be untrue. Combining ex situ (i.e., after the deposition of the monolayer on the solid substrate) with in situ analysis – revealed significant changes in the microstructure . This study covers only micron-sized core-shell NCs.…”

Core-softened colloid under extreme geometrical confinement

“…Many core-softened (CS) approaches have been proposed to model these complex fluids, including ramp-like, square and ramp shoulders, exponential, Hertzian, multi-Hertzian, and Gaussian potentials. 33–42 For instance, in the work by Grillo and co-authors, 5 a Hertzian potential was employed to reproduce the distinct patterns observed in soft colloids at liquid–liquid interfaces. Interestingly, they found that a key ingredient to observe a large variety of micropatterns is to first immobilize two layers of colloids onto a solid substrate one after the other.…”