Search

The adsorption of ellipsoidal colloidal particles on liquid interfaces induces interfacial deformation, resulting in anisotropic interface-mediated interactions and the formation of superstructures. Soft prolate-shaped microgels at the air-water interface offer an ideal model for studying spontaneous capillary-driven self-assembly due to their tunable aspect ratio, controlled functionality, and softness. These microgels consist of a polystyrene core surrounded by a cross-linked, fluorescently labeled poly(Nisopropylmethylacrylamide) shell. By uniaxially stretching the particles embedded in polyvinyl alcohol films, the aspect ratio ρ can be finely adjusted. ρ was found to vary from 1 to 8.8 as estimated in their swollen conformation at 20 °C from confocal laser scanning microscopy. The spontaneous interfacial self-assembly at the air-water interface is investigated through fluorescence microscopy, theoretical calculations, and computer simulations. A structural transition occurs from a seemingly random assembly for small aspect ratios to compact clusters, which transform into a side-to-side assembly forming long chains for high aspect ratios. The influence of the poly(N-isopropylmethacrylamide) shell on the assembly indicates a significant ρ-dependent microgel deformation. This deformation, in turn, determines the average distance between the particles. Consequently, capillary-driven self-assembly of soft anisotropic colloids becomes a powerful mechanism for structuring interfaces and designing microstructured materials. [ABSTRACT FROM AUTHOR]

Soft colloidal macromolecular structures with programmable chemical functionalities, size, and shape are important building blocks for the fabrication of catalyst systems and adaptive biomaterials for tissue engineering. However, the development of the easy upscalable and template‐free synthesis methods to obtain such colloids lack in understanding of molecular interactions that occur in the formation mechanisms of polymer colloids. Herein, a computer simulation‐driven experimental synthesis approach based on the supramolecular self‐assembly followed by polymerization of tailored pyrazole‐modified monomers is developed. Simulations for a series of pyrazole‐modified monomers with different numbers of pyrazole groups, different length and polarity of spacers between pyrazole groups and the polymerizable group are first performed. Based on simulations, monomers able to undergo π–π stacking and guide the formation of supramolecular bonds between polymer segments are synthesized and these are used in precipitation polymerization to synthesize anisotropic microgels. This study demonstrates that microgel morphologies can be tuned from spherical, raspberry‐like to dumbbell‐like by the increase of the pyrazole‐modified monomer loading, which is concentrated at periphery of growing microgels. Combining experimental and simulation results, this work provides a quantitative and predictive approach for guiding microgel design that can be further extended to a diversity of colloidal systems and soft materials with superior properties. [ABSTRACT FROM AUTHOR]

Densely grafted comb-like macromolecules (bottlebrushes) with alternating solvophobic and solvophilic side chains were studied in a selective solvent and at the liquid interface using mesoscopic computer simulations. The effects of backbone length and copolymer composition were considered. While self-assembly in solution revealed only spherical aggregates for all ar-chitectures studied, adsorption onto the liquid interface in particular cases resulted in morpho-logical changes, with worm-like aggregates or a continuous monolayer observed. In turn, the compression of macromolecules at the interface also leads to morphological transitions, includ-ing the formation of a mesh-like percolated structure. The obtained results may be useful for the preparation of solid nanoparticles of anisotropic shape or nanostructured ultra-thin copolymer films. [ABSTRACT FROM AUTHOR]

Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli‐responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus‐like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self‐assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus‐like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions. [ABSTRACT FROM AUTHOR]

Rarely polymer-grafted nanoparticles are shown to be able to self-assemble into stable nanostructures of different morphologies. The driving force for the assembly is a competition between a short-range attraction of the nanoparticles and long-range repulsion of the grafted chains. Effects of the solvent quality for the nanoparticles, grafting density and the length of the chains are studied. We have shown that non-spherical vesicles resembling a monocrystal can be stable in dilute solution. In them, the wall represents a sheet of hexagonally packed nanoparticles which sharply bends to become closed forming facets and edges. Improving solvent quality leads to a cascade of transitions: vesicles - tubes - perforated sheets - threads. Adsorption of the nanoparticles on a solvophobic surface can result in their 2D self-assembly. We have predicted ordering of the nanoparticles into a hexagonal network similar to the structure of graphene sheets. Schematic diagrams of states in 2D and 3D are constructed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Computer simulations demonstrate stability of various self-assembled morphologies in aqueous solutions of surfactants. • Small fractions of oil in the solution are absorbed in the aggregates' interior. • Oil absorption by the worm-like micelles leads to their decomposition into the spherical micelles. • Vesicles and lamellae transform into nanofoam-like structure (oil- and water-rich voids) upon addition of oil. Addition of small portions of oil in aqueous solutions of surfactants self-assembled into different morphologies is studied with computer simulations. Uptake of oil by the spherical micelles leads to their swelling, decrease in the number of the micelles which keep their spherical shape. On the contrary, initial self-similar (keeping elongated shape) swelling of cylindrical micelles takes turn by their decomposition into the spherical micelles caused by the Rayleigh instability upon increase of the oil concentration. As a result, the number of the micelles in the system non-monotonously changes with oil concentration: initial growth in the number is followed by the diminishing. Vesicular and lamellar solutions are shown to reveal quite different behavior. At first, the wall thickness of the vesicles and lamellae increases due to the up-taken oil which leads to enlargement of the vesicles in the solution. Then, the vesicles aggregate forming nanofoam-like structure: nanobubbles are glued in the foam by means of oil-rich domains. Similar behavior is observed for the lamellar structure, when some of the lamellae bend and bind with neighbor ones creating isolated water- and oil-rich domains. We can expect that in contrast to the cylindrical micelles, whose viscosity dramatically decreases with the increase of the oil concentration, vesicular and lamellar solutions behave oppositely increasing viscosity upon addition of oil. [ABSTRACT FROM AUTHOR]