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37 results on '"Rudov, Andrey A."'

1. Drying of Soft Colloidal Films

Author

Kuk, Keumkyung, Ringling, Julian, Gräff, Kevin, Hänsch, Sebastian, Carrasco-Fadanelli, Virginia, Rudov, Andrey A., Potemkin, Igor I., von Klitzing, Regine, Buttinoni, Ivo, and Karg, Matthias

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

Thin films made of deformable micro- and nano-units, such as biological membranes, polymer interfaces, and particle-laden liquid surfaces, exhibit a complex behavior during drying, with consequences for various applications like wound healing, coating technologies, and additive manufacturing. Studying the drying dynamics and structural changes of soft colloidal films thus holds the potential to yield valuable insights to achieve improvements for applications. In this study, we employ interfacial monolayers of core-shell microgels with varying degrees of softness as model systems and investigate their drying behavior on differently modified solid substrates (hydrophobic vs. hydrophilic). By leveraging on video microscopy, particle tracking, and thin film interference, we shed light on the interplay between microgel adhesion to solid surfaces and the immersion capillary forces that arise in the thin liquid film. We discovered that a dried replica of the interfacial microstructure can be more accurately achieved on a hydrophobic substrate relative to a hydrophilic one, particularly when employing softer colloids as opposed to harder counterparts. These observations are qualitatively supported by experiments with a thin film pressure balance which allows mimicking and controlling the drying process and by computer simulations with coarse-grained models., Comment: 36 pages of main manuscript with 9 figures and 1 table, 22 pages of Supporting Information with 21 figures and 4 tables

Published
2024
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2. Interfacial assembly of anisotropic core-shell and hollow microgels

Author

Nickel, Anne C., Rudov, Andrey A., Potemkin, Igor I., Crassous, Jérôme J., and Richtering, Walter

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

Microgels, cross-linked polymers with submicrometer size, are ideal soft model systems. While spherical microgels have been studied extensively, anisotropic microgels have been hardly investigated. In this study, we compare the interfacial deformation and assembly of anisotropic core-shell and hollow microgels. The core-shell microgel consists of an elliptical core of hematite covered with a thin silica layer and a thin shell made of PNiPAM. The hollow microgels were obtained after a two step etching procedure of the inorganic core. The behavior of these microgels at the oil-water interface was investigated in a Langmuir Blodgett trough combined with ex-situ AFM. First, the influence of the architecture of anisotropic microgels on their spreading at the interface was investigated experimentally and by dissipative particle dynamic simulations. Hereby, the importance of the local shell thickness on the lateral and longitudinal interfacial deformation was highlighted as well as the differences between the core-shell and hollow architectures. The shape of the compression isotherms as well as the dimensions, ordering and orientation of the microgels at the different compressions were analysed. Due to their anisotropic shape and stiffness, both anisotropic microgels were found to exhibit significant capillary interactions with a preferential side-to-side assembly leading to stable microgel clusters at low interfacial coverage. Such capillary interactions were found to decrease in the case of the more deformable hollow anisotropic microgels. Consequently, anisotropic hollow microgels were found to distribute more evenly at high surface pressure compared to stiffer core-shell microgels. Our findings emphasize the complex interplay between the colloid design, anisotropy and softness on the interfacial assembly and the opportunities it thus offers to create more complex ordered interfaces.

Published
2022
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3. Anisotropic Microgels show their Soft Side

Author

Nickel, Anne C., Kratzenberg, Timon, Bochenek, Steffen, Schmidt, Maximilian M., Rudov, Andrey A., Falkenstein, Andreas, Potemkin, Igor I., Crassous, Jérôme J., and Richtering, Walter

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

Anisotropic, submicrometer sized particles are versatile systems providing interesting features in creating ordering in 2-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 a rich 2D phase behavior and show how softness affects the ordering of anisotropic particles at fluid oil-water interfaces. Three different core-shell systems were synthesized such that they have the same elliptical hematite-silica core but differ with respect to thickness and stiffness of the soft microgel shell. Compression isotherms, the shape of individual core-shell microgel as well as their 2D order at a decane-water interface are investigated by means of the Langmuir-Blodgett technique combined with ex-situ Atomic Force Microscopy (AFM) imaging, as well as by Disspiative Particle Dynamics (DPD) simulations. We show how softness, size and anisotropy of the microgel shell affect the side-to-side vs. tip-to-tip ordering of anisotropic hybrid microgels as well as the alignment with respect to the direction of compression in the Langmuir trough. A large and soft microgel shell leads to an ordered structure with a tip-to-tip alignment directed perpendicular to the direction of compression. In contrast, a thin and harder microgel shell leads to side-to-side ordering orientated parallel to the compression direction. In addition, the thin and harder microgel shell induces clustering of the microgels in the dilute state indicating the presence of strong capillary interactions. Our findings highlight the relevance of softness for the complex ordering of anisotropic hybrid microgels at interfaces.

Published
2021
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8. Anisotropic Microgels Show Their Soft Side

Author

Nickel, Anne C., primary, Kratzenberg, Timon, additional, Bochenek, Steffen, additional, Schmidt, Maximilian M., additional, Rudov, Andrey A., additional, Falkenstein, Andreas, additional, Potemkin, Igor I., additional, Crassous, Jérôme J., additional, and Richtering, Walter, additional

Published
2021
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11. Communication: Intraparticle segregation of structurally homogeneous polyelectrolyte microgels caused by long-range Coulomb repulsion.

Author

Rumyantsev, Artem M., Rudov, Andrey A., and Potemkin, Igor I.

Subjects
*POLYELECTROLYTES, *MICROGELS, *AQUEOUS solutions, *ENTROPY, *MONOVALENT cations, *SOLVENTS
Abstract

Structurally homogeneous polyelectrolyte microgels in dilute aqueous solutions are shown to exhibit inhomogeneous density profile including intraparticle "phase" coexistence of hollow core and dense "skin." This effect is a consequence of long-range Coulomb repulsion of charged groups which appear because of entropy-driven escape of monovalent counterions into the outer solvent. Excess of the charged groups at the periphery of the microgel particle reduces electrostatic energy and overall free energy of the system despite a penalty in the elastic free energy of strongly stretched subchains in the hole. This finding can serve as additional tool controlling encapsulation, transport, and release of high- and low-molecular-weight species in processes where the microgels are used as delivery systems. [ABSTRACT FROM AUTHOR]

Published
2015
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12. Back Cover: Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization (Angew. Chem. Int. Ed. 3/2020)

Author

Xu, Wenjing, primary, Rudov, Andrey, additional, Oppermann, Alex, additional, Wypysek, Sarah, additional, Kather, Michael, additional, Schroeder, Ricarda, additional, Richtering, Walter, additional, Potemkin, Igor I., additional, Wöll, Dominik, additional, and Pich, Andrij, additional

Published
2019
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13. Rücktitelbild: Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization (Angew. Chem. 3/2020)

Author

Xu, Wenjing, primary, Rudov, Andrey, additional, Oppermann, Alex, additional, Wypysek, Sarah, additional, Kather, Michael, additional, Schroeder, Ricarda, additional, Richtering, Walter, additional, Potemkin, Igor I., additional, Wöll, Dominik, additional, and Pich, Andrij, additional

Published
2019
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17. Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization.

Author

Xu, Wenjing, Rudov, Andrey, Oppermann, Alex, Wypysek, Sarah, Kather, Michael, Schroeder, Ricarda, Richtering, Walter, Potemkin, Igor I., Wöll, Dominik, and Pich, Andrij

Subjects
*MICROGELS, *COACERVATION, *POLYMERIZATION, *AQUEOUS solutions, *PRECIPITATION (Chemistry), *COLLOID synthesis
Abstract

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]

Published
2020
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35. Structural Changes in Lamellar Diblock Copolymer ThinFilms upon Swelling in Nonselective Solvents.

Author

Rudov, Andrey A., Patyukova, Elena S., Neratova, Irina V., Khalatur, Pavel G., Posselt, Dorthe, Papadakis, Christine M., and Potemkin, Igor I.

Subjects
*BLOCK copolymers, *SWELLING of materials, *POLYMER structure, *MOLECULAR dynamics, *SOLVENTS, *PARTICLE size distribution
Abstract

Using dissipative particle dynamicssimulations, we study the swellingof lamellae-forming diblock copolymer films in a nonselective solvent.Both the parallel and the perpendicular orientations of lamellae inthe film are studied. The swelling of the film with parallel lamellaeis accompanied by an increase of their number. In doing so, the lamellarthickness reveals nonmonotonous behavior: affine growth (low degreeof solvent uptake) is succeeded by a decrease in thickness (high degreeof solvent uptake). Whereas the first regime reflects a finite size(film thickness) effect, the decrease is a more common effect, whichis also valid for perpendicular lamellae, and is due to shrinkageof the diblock copolymers due to the shielding of unfavorable AB contactsby the solvent molecules. The film swelling leads to an increase ofthe number of perpendicular lamellae as well. However, such an increaseis only possible if the film at first is dissolved and then condensedabsorbing a certain amount of solvent. Otherwise, splitting of thelamellae requires a large-scale mass transport which is realizableneither in modeling nor in experiment. Instead of splitting, the perpendicularlamellae can tilt upon swelling. This process is much faster and satisfiesthe space-filling condition at the thinning of the lamellae. Thatis why tilted lamellae are often observed in experiments and computersimulations. We demonstrate also that the distribution of the absorbedsolvent in the film is inhomogeneous with a maximum at the AB interfaces.The kinetics of the parallel lamellae swelling is compared with experimentaldata. [ABSTRACT FROM AUTHOR]

Published
2013
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36. Rücktitelbild: Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization (Angew. Chem. 3/2020).

Author

Xu, Wenjing, Rudov, Andrey, Oppermann, Alex, Wypysek, Sarah, Kather, Michael, Schroeder, Ricarda, Richtering, Walter, Potemkin, Igor I., Wöll, Dominik, and Pich, Andrij

Subjects
*MICROGELS, *COACERVATION, *POLYMERIZATION, *PRECIPITATION (Chemistry)
Abstract

Rücktitelbild: Synthesis of Polyampholyte Janus-like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization (Angew. Die Mischzeit der zwei Lösungen wachsender Mikrogel-Vorläufer bestimmt die Morphologie der Polyampholyt-Mikrogele. Janus-artige Mikrogele, Molekulare Modellierung, Polyampholyte, Responsive Materialien, Selbstassemblierung. [Extracted from the article]

Published
2020
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