Self-Assembly of Ionic Microgels Driven by an Alternating Electric Field: Theory, Simulations, and Experiments

The structural properties of a system of ionic microgels under the influence of an alternating electric field are investigated both theoretically and experimentally. This combined investigation aims to shed light on the structural transitions that can be induced by changing either the driving freque...

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Published inACS nano Vol. 12; no. 5; pp. 4321 - 4337
Main Authors Colla, Thiago, Mohanty, Priti S, Nöjd, Sofi, Bialik, Erik, Riede, Aaron, Schurtenberger, Peter, Likos, Christos N
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 22.05.2018
Subjects
chain formation
Chemical Sciences
coarse-graining
confocal microscopy
dipoles
Fysikalisk kemi
ionic microgels
Kemi
Natural Sciences
Naturvetenskap
Physical Chemistry
self-assembly
soft colloids
self-assembly
chain formation
ionic microgels
confocal microscopy
coarse-graining
soft colloids
dipoles
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Summary:The structural properties of a system of ionic microgels under the influence of an alternating electric field are investigated both theoretically and experimentally. This combined investigation aims to shed light on the structural transitions that can be induced by changing either the driving frequency or the strength of the applied field, which range from string-like formation along the field to crystal-like structures across the orthogonal plane. In order to highlight the physical mechanisms responsible for the observed particle self-assembly, we develop a coarse-grained description, in which effective interactions among the charged microgels are induced by both equilibrium ionic distributions and their time-averaged hydrodynamic responses to the applied field. These contributions are modeled by the buildup of an effective dipole moment at the microgels backbones, which is partially screened by their ionic double layer. We show that this description is able to capture the structural properties of this system, allowing for very good agreement with the experimental results. The model coarse-graining parameters are indirectly obtained via the measured pair distribution functions and then further assigned with a clear physical interpretation, allowing us to highlight the main physical mechanisms accounting for the observed self-assembly behavior.
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ISSN:1936-0851
1936-086X
DOI:10.1021/acsnano.7b08843