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Compression and Interpenetration of Ionic Microgels in Electrostatically Self-Assembled Clusters
Alexander V Petrunin1,2, Hannah F Mathews3,4, Tom Höfken2
1Institute of Experimental Physics of Condensed Matter, Heinrich-Heine University, Universitätsstr. 1, Düsseldorf 40225, Germany.
ACS Nano
|July 27, 2026
Summary
Soft microgels compress dramatically when oppositely charged particles assemble into clusters. This shell compression, driven by counterion release, alters individual colloid structure and impacts hierarchical material assembly.
Area of Science:
- Soft matter physics
- Materials science
- Colloid science
Background:
- Colloidal self-assembly offers tunable material properties like softness and porosity.
- Soft building blocks significantly alter assembly characteristics compared to hard particles.
- The behavior of individual soft colloids within assemblies remains poorly understood.
Purpose of the Study:
- To investigate the structural changes of individual soft microgels during cluster formation.
- To understand the mechanism behind microgel deformation in oppositely charged assemblies.
- To elucidate how individual colloid structure influences hierarchical assembly.
Main Methods:
- Utilized small-angle neutron scattering (SANS) with contrast variation.
- Complemented SANS with small-angle X-ray scattering (SAXS).
- Employed molecular dynamics (MD) simulations for mechanistic insights.
Main Results:
- Observed significant compression of the microgel fuzzy shell, forming a distinct core-shell architecture.
- Contrastingly, similarly charged microgels exhibited osmotic deswelling.
- MD simulations revealed increased polymer density at contact points due to entropically driven counterion release.
Conclusions:
- Oppositely charged microgels compress their shells or interpenetrate to maximize counterion release.
- The structure of individual soft colloids is significantly altered during cluster assembly.
- These alterations in colloid structure impact the properties of the larger hierarchical assembly.
