Compression and Interpenetration of Ionic Microgels in Electrostatically Self-Assembled Clusters

ACS Nano, vol. 20, pp. 21599–21614

Abstract

Colloidal self-assembly is a powerful strategy to obtain materials with desired softness, porosity and biocompatibility. When soft building blocks are used, these properties can change dramatically, compared to materials produced using hard particles. However, the fate of individual colloids inside these assemblies is not fully understood. Here, asymmetric mixtures of soft microgels with opposite electrical charges are used as model building blocks to assemble colloidal clusters. The changes in the form factor of individual microgels due to cluster formation are analyzed using small-angle neutron scattering with contrast variation, complemented with small-angle X-ray scattering and molecular dynamics simulations. A strong compression of the fuzzy shell of a microgel is observed, which results in a peculiar core-shell architecture of the microgel. In contrast, a reference system of similarly charged microgels shows osmotic deswelling in both the dense core and fuzzy shell, as expected. Molecular dynamics simulations reveal that the polymer density at contact between the oppositely charged microgels increases due to the entropically favorable counterion release. To maximize the number of released counterions, the microgels compress their shells or interpenetrate each other. The results show that the structure of individual soft colloids may be significantly altered during the assembly of clusters, which can influence the larger hierarchical assembly.

Authors 9

1. Alexander V. Petrunin Aachen

   Heinrich Heine University Düsseldorf · RWTH Aachen University

   Affiliation as printed

   Heinrich-Heine University , , Universitätsstr. 1 , ,

   RWTH Aachen University , , Landoltweg 2 , ,

2. Hannah F. Mathews Aachen DWI-Leibniz-Institute for Interactive Materials e.V

   DWI – Leibniz Institute for Interactive Materials · RWTH Aachen University

   Affiliation as printed

   DWI - Leibniz Institute for Interactive Materials e. V. , Forckenbeckstr. 50 , ,

   RWTH Aachen University , , Worringerweg 2 , ,

3. Tom Höfken Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University , , Landoltweg 2 , ,

4. Philipp Leclercq Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University , , Landoltweg 2 , ,

5. Ralf Schweins

   Institut Laue-Langevin

   Affiliation as printed

   Institut Laue-Langevin ILL , DS/LSS, 71 Avenue des Martyrs , ,

6. Pablo Mota‐Santiago

   Australian Nuclear Science and Technology Organisation · Lund University · Australian Synchrotron

   Affiliation as printed

   Australian Synchrotron, ANSTO , , ,

   Lund University , , ,

7. Stefanie Schneider Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University , , Landoltweg 2 , ,

8. Andrij Pich Aachen DWI-Leibniz-Institute for Interactive Materials e.V

   Maastricht University · DWI – Leibniz Institute for Interactive Materials · RWTH Aachen University

   Affiliation as printed

   DWI - Leibniz Institute for Interactive Materials e. V. , Forckenbeckstr. 50 , ,

   Maastricht University , , ,

   RWTH Aachen University , , Worringerweg 2 , ,

9. Andrea Scotti

   Lund University

   Affiliation as printed

   Lund University , , ,