Hollow microgels squeezed in overcrowded environments

microgel blue Walter Richtering

A. Scotti, M. Brugnoni, A. A. Rudov, J. E. Houston, I. I. Potemkin, and W. Richtering

The Journal of Chemical Physics 148, 174903 (2018)

We study how a cavity changes the response of hollow microgels with respect to regular ones in
overcrowded environments. The structural changes of hollowpoly(N-isopropylacrylamide) microgels
embedded within a matrix of regular ones are probed by small-angle neutron scattering with contrast
variation. The form factors of the microgels at increasing compressions are directly measured. The
decrease of the cavity size with increasing concentration shows that the hollow microgels have an
alternative way with respect to regular cross-linked ones to respond to the squeezing due to their
neighbors. The structural changes under compression are supported by the radial density profiles
obtained with computer simulations. The presence of the cavity offers to the polymer network the
possibility to expand toward the center of the microgels in response to the overcrowded environment.
Furthermore, upon increasing compression, a two step transition occurs: First the microgels are
compressed but the internal structure is unchanged; then, further compression causes the fuzzy shell
to collapse completely and reduce the size of the cavity. Computer simulations also allow studying
higher compression degrees than in the experiments leading to the microgel’s faceting.



Anionic shell shields a cationic core allowing for uptake and release of polyelectrolytes within core-shell responsive microgels

pic showing polyelectrolyte A. Gelissen  

Probing the Internal Heterogeneity of Responsive Microgels Adsorbed to an Interface by a Sharp SFM Tip: Comparing Core-Shell and Hollow Microgels

pic showing microgel M. F. Schulte  

Swelling of a Responsive Network within Different Constraints in Multi-Thermosensitive Microgels

pic showing microgel M. Brugnoni  

How do microgels collapse?

microgel collapsing Walter Richtering

Time-resolved structural evolution during the collapse of responsive hydrogels: The microgel-to-particle transition

R. Keidel , A. Ghavami, D.M. Lugo, G. Lotze, O. Virtanen, P. Beumers, J.S. Pedersen, A. Bardow, R.G. Winkler and W. Richtering

Science Advances 06 Apr 2018:
Vol. 4, no. 4, eaao7086
DOI: 10.1126/sciadv.aao7086

The structural adaption of microgels to the environment involves a unique transition from a flexible, swollen finite-size macromolecular network, characterized by a fuzzy surface, to a colloidal particle with homogeneous density and a sharp surface. In this contribution, we determine, for the first time, the structural evolution during the microgel-to-particle transition. Time-resolved small-angle x-ray scattering experiments and computer simulations unambiguously reveal a two-stage process: In a first, very fast process, collapsed clusters form at the periphery, leading to an intermediate, hollowish core-shell structure that slowly transforms to a globule. This structural evolution is independent of the type of stimulus and thus applies to instantaneous transitions as in a temperature jump or to slower stimuli that rely on the uptake of active molecules from and/or exchange with the environment. The fast transitions of size and shape provide unique opportunities for various applications as, for example, in uptake and release, catalysis, or sensing.

Interview & Video


  Cover of the journal PCCP 19 2017 showing Lucio Isa

Compression and deposition of microgel monolayers from fluid interfaces: particle size effects on interface microstructure and nanolithography

L. Scheidegger, M.A. Fernandez-Rodriguez, K. Geisel, M. Zanini, R. Elnathan, W. Richtering and L. Isa
Physical Chemistry Chemical Physics, 2017, 19(13), 8671-8680.

Controlling the microstructure of monolayers of microgels confined at a water/oil interface is the key to their successful application as nanolithography masks after deposition on a solid substrate. Previous work demonstrated that compression of the monolayer can be used to tune the microgel arrangement and to explore the full two-dimensional area–pressure phase diagram of the particles trapped at the interface. Here, we explore a new size range, using microgels with 210 nm and 1.45 μm bulk diameters, respectively.


  Cover ACS Special Issue 2017

Plamper, F. A.; Richtering, W. Functional Microgels and Microgel Systems. Accounts of Chemical Research 2017, 50, 131–140


  Microgels enable capacious uptake Walter Richtering

Microgels enable capacious uptake and controlled release of architecturally complex macromolecular species

Stefan Walta, Dmitry V. Pergushov, Alex Oppermann, Alexander A. Steinschulte, Karen Geisel, Larisa V. Sigolaeva, Felix A. Plamper, Dominik Wöll, Walter Richtering, Polymer 119 (2017) 50-58, DOI: 10.1016/j.polymer.2017.05.008

Abstract:This study highlights the use of microgels as containers of high capacity for uptake and triggered release of multi-functional guests. As a model guest, heteroarm star-shaped copolymers (miktoarm stars) are chosen, as their certain arms could carry different active moieties, while other arms could act as “stickers” to the microgel host. The miktoarm stars are able to penetrate into the microgels to compensate their negatively charged groups.. Furthermore, a jump-wise increase of ionic strength in solutions of the complexes triggers the complete release of the miktoarm stars from the microgel, and the system stays always colloidally stable. Thus, microgel-based polylectrolyte complexes provide opportunities for many important applications, especially in targeted/controlled delivery.


  Functional Microgels und Microgelsystems AK Richtering

Functional Microgels and Microgel Systems

F. A. Plamper and W. Richtering
Acc. Chem. Res., 2017, 50(2), 131-140.

Microgels unite properties of very different classes of materials. They allow combining features of chemical functionality, structural integrity, macromolecular architecture, adaptivity, permeability, and deformability in a unique way to include the "best" of the colloidal, polymeric and surfactant worlds. This will open the door for novel applications in very different fields such as, e.g., in sensors, catalysis, and separation technology.

DOI: 10.1021/acs.accounts.6b00544


  Illustration for paper Dominik Wöll

3D Structures of Responsive Nanocompartmentalized Microgels

A. P. H. Gelissen, A. Oppermann, T. Caumanns, P. Hebbeker, S. K. Turnhoff, R. Tiwari, S. Eisold, U. Simon, Y. Lu, J. Mayer, W. Richtering, A. Walther, D. Wöll
Nano Letters, 2016.

A combination of in situ electron microscopy and superresolved fluorescence localization microscopy allows for a determination of 3D compartmentalization of core-shell microgel structures. A software package to evaluate 2D microscopy images to obtain 3D structures is provided.

DOI: 10.1021/acs.nanolett.6b03940



The Next Step in Precipitation Polymerization of N-Isopropylacrylamide: Particle Number Density Control by Monochain Globule Surface Charge Modulation.

O. L. J. Virtanen, M. Brugnoni, M. Kather, A. Pich, W. Richtering
Polymer Chemistry, 2016, 7, 5123-5131.

DOI: 10.1039/C6PY01195K


  Multi-Shell Hollow Nanogels with Responsive Shell Permeability AK Richtering

Multi-Shell Hollow Nanogels with Responsive Shell Permeability

A. J. Schmid, J. Dubbert, A. A. Rudov, J. S. Pedersen, P. Lindner, M. Karg, I. I. Potemkin and W. Richtering
Scientific Reports, 2016, 6, Article number: 22736.

DOI: 10.1038/srep22736



Persulfate Initiated Ultra-Low Cross-Linked Poly(N-Isopropylacrylamide) Microgels Possess an Unusual Inverted Cross-Linking Structure

O. L. J. Virtanen, A. Mourran, P. T. Pinard, W. Richtering
Soft Matter 2016, 12, 3919–3928.
DOI: 10.1039/C6SM00140H

  Hollow and Core–Shell Microgels at Oil–Water Interfaces

Hollow and Core–Shell Microgels at Oil–Water Interfaces: Spreading of Soft Particles Reduces the Compressibility of the Monolayer

K. Geisel, A. A. Rudov, I. I. Potemkin and W. Richtering
Langmuir, 2015, 31 (48),13145–13154.
DOI: 10.1021/acs.langmuir.5b03530


JARA-SOFT: Soft Matter Science made in Aachen und Jülich

Sixt JARA-Section starts wirth great kick-off
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  Core–Shell–Shell and Hollow Double-Shell Microgels with Advanced Temperature Responsiveness

Core–Shell–Shell and Hollow Double-Shell Microgels with Advanced Temperature Responsiveness

Janine Dubbert, Katja Nothdurft, Matthias Karg and Walter Richtering
Macromol. Rapid Commun., 2015, 36(2), 159-164.
DOI: 10.1002/marc.201400495

  Methanol-induced change

Methanol-induced change of the mechanism of the temperature- and pressure-induced collapse of N-Substituted acrylamide copolymers

Christian H. Hofmann, Sebastian Grobelny, Paweł T. Panek, Laura K. M. Heinen, Ann-Kristin Wiegand, Felix A. Plamper, Christoph R. Jacob, Roland Winter and Walter Richtering
Journal of Polymer Science Part B: Polymer Physics, 53(7), 532-544, 2015.
DOI: 10.1002/polb.23676

  Effect of the Molecular Architecture

Effect of the Molecular Architecture on the Internal Complexation Behavior of Linear Copolymers and Miktoarm Star Polymers

Pascal Hebbeker, Felix A. Plamper and Stefanie Schneider
Macromolecular Theory and Simulations, 2015.
DOI: 10.1002/mats.201400077

  How Hollow Are Thermoresponsive Hollow Nanogels?

How Hollow Are Thermoresponsive Hollow Nanogels?

Janine Dubbert et al.
Macromolecules, 47 (24), 8700–8708, 2014.

DOI: 10.1021/ma502056y

  Highly ordered 2D microgel arrays

Highly ordered 2D microgel arrays: compression versus self-assembly

Karen Geisel, Walter Richtering and Lucio Isa
Soft Matter, 10, 7968-7976, 2014. DOI: 10.1039/C4SM01166J
2014 Soft Matter Hot Papers