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@PHDTHESIS{Strauch:1022281,
author = {Strauch, Christian},
othercontributors = {Richtering, Walter and Reščič, Jurij},
title = {{M}odeling and {M}onte {C}arlo simulations of polyampholyte
microgels with complex structures},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-09914},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2026; Dissertation, RWTH Aachen University, 2025},
abstract = {Microgels are three-dimensional crosslinked polymer
networks, ranging in size from nanometers to micrometers,
that are swollen by a solvent. They exhibit responsiveness
to external stimuli such as temperature, pH, ionic strength,
and magnetic fields. For biomedical applications, such as
drug delivery, polyampholyte microgels are particularly
promising due to their ability to safely transport drugs to
target sites and release them through charge reversal
triggered by pH changes. This thesis uses Metropolis Monte
Carlo simulations to investigate the ionization and swelling
behavior of polyelectrolyte and polyampholyte microgels and
their capacity to take up guest molecules. A parallelized
algorithm developed in this work enables the simulation of
more complex topologies, such as core-shell structures, and
allows for simulations at higher ionic strengths. The
microgel models used in this thesis are based on a
coarse-grained model, providing results in qualitative
agreement with experimental findings. By systematically
varying parameters like pK values, microgel concentration,
and ionic strength around a reference system, the influence
of these parameters on macroscopic properties, such as the
degree of ionization and the radius of gyration, is
determined. Additionally, the simulations provide insights
into properties that are difficult to obtain experimentally,
such as the degree of ionization for both acids and bases
within the same microgel, and microscopic information,
including local ionization within the microgels. Simulations
of core-shell polyampholyte microgels show that the width of
the U-shaped swelling curve as a function of pH depends on
the relative dissociation constants of acidic and basic
monomers. The addition of salt narrows this swelling
transitions. Furthermore, microgel swelling correlates
approximately linearly with the total network charge.
Simulations involving polyelectrolyte and polyampholyte
microgels with various types of guest molecules demonstrate
the capability of these microgels to take up such molecules.
In particular, the model for oligopeptide uptake in
polyelectrolyte microgels shows promise for future
investigations in combination with experimental studies.
Finally, the constant pH method in the canonical ensemble is
critically evaluated following criticisms about the approach
being implicitly grand-canonical. While titration curves
obtained with this method and the reaction ensemble method
show significant differences for colloidal particles, they
differ only at low degrees of ionization for polyelectrolyte
microgels. The results demonstrate that the constant pH
method provides a reliable and practical approach for the
microgels simulated in this thesis.},
cin = {153310 / 150000},
ddc = {540},
cid = {$I:(DE-82)153310_20140620$ / $I:(DE-82)150000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-09914},
url = {https://publications.rwth-aachen.de/record/1022281},
}
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