{"id":{"repo_id":"freiburg-diss","oai_identifier":"oai:freidok.uni-freiburg.de:1687"},"canonical_url":"https://search.dev.ndltd.org/etd/freiburg-diss/oai:freidok.uni-freiburg.de:1687","repository":{"repo_id":"freiburg-diss","name":"University of Freiburg","base_url":"https://freidok.uni-freiburg.de/oai/oai2.php"},"display":{"title":"Weak polyacid brushes : synthesis, swelling behavior, complex formation and micropatterning","abstract":"In this work, densely end-grafted polymer monolayers, so-called \"polymer brushes\", were covalently attached to solid planar surfaces and investigated with respect to their properties in contact with aqueous solutions of varying composition.
The synthesis of these polymer brushes was performed in two steps. First, an end-functionalized azoinitiator was covalently anchored to silicon wafers and planar glass substrates to form a self-assembled monolayer. Then, a surface-initiated free radical polymerization of vinyl monomers was triggered by thermal cleavage of the initiator (\"grafting from\" polymerization). By varying the monomer concentration and the polymerization time, the molecular weight of the surface-attached polymer chains and the anchoring density, a characteristic parameter that determines the degree of chain stretching of a polymer brush, could be reproducibly adjusted. Furthermore, different photopatterning strategies were implemented into the concept of surface-initiated polymerization. Using different approaches, positive and negative images of a mask and, in particular, laterally chemically microstructured polymer brushes could be obtained.
The focus of this work was on the investigation of the properties of poly(methacrylic acid) (PMAA) brushes, a weak polyelectrolyte whose charge density can be tuned by adjustment of external parameters such as the solution pH-value. The PMAA brushes were swollen in aqueous solutions of different ionic composition and their properties were studied as a function of the valency, size (polarizability), concentration and nature of the ion. In another study, the complex formation of PMAA brushes with oppositely charged surfactants of different alkyl chain lengths was investigated. Stable complexes were formed with multivalent cations and oppositely charged surfactants. The complex formation behavior of PMAA brushes in contact with various small metal ion and oppositely charged surfactant solutions was investigated in detail, both, through in situ and ex situ measurements and significant new insights into the complex formation mechanism in such systems could be obtained. In particular, it was shown that already trace concentrations of certain ions and surfactants are sufficient to strongly alter the conformation of surface-attached molecules. This results in a strong modification of the layer properties such as the accessibility of functional groups. On the other side, seemingly small variations in the chemical details, such as interchanging the two divalent cations magnesium and copper which have the same charge and similar ionic radii, can have tremendous effects on the way these ions affect the polyelectrolyte brush structure. Moreover, these systems do not always behave as one would intuitively expect. For instance, the influence of monovalent silver ions on the weak polyacid brush structure is much closer related to that of divalent calcium ions than to that of monovalent sodium ions.
These findings have important implications for the fundamental understanding of biological processes such as signaling, bioadhesion or the stabilization of micelles as in many biological systems (surface) biopolymers adopt constrained conformations similar to those of polymer brushes and a mix of different ions is usually present. Moreover, an understanding of the influence of certain ions on the molecular structure of thin surface-bound polyelectrolyte brushes is crucial for technological applications such as the electrosteric stabilization of colloids, the preparation of surfaces with ultra low friction properties or for the development of novel materials for drug delivery, biosensor or nanoreactor applications which rely on the fact that many proteins bind to such systems under preservation of their natural structure.","abstract_html":"In this work, densely end-grafted polymer monolayers, so-called "polymer brushes", were covalently attached to solid planar surfaces and investigated with respect to their properties in contact with aqueous solutions of varying composition. <br> <br>The synthesis of these polymer brushes was performed in two steps. First, an end-functionalized azoinitiator was covalently anchored to silicon wafers and planar glass substrates to form a self-assembled monolayer. Then, a surface-initiated free radical polymerization of vinyl monomers was triggered by thermal cleavage of the initiator ("grafting from" polymerization). By varying the monomer concentration and the polymerization time, the molecular weight of the surface-attached polymer chains and the anchoring density, a characteristic parameter that determines the degree of chain stretching of a polymer brush, could be reproducibly adjusted. Furthermore, different photopatterning strategies were implemented into the concept of surface-initiated polymerization. Using different approaches, positive and negative images of a mask and, in particular, laterally chemically microstructured polymer brushes could be obtained. <br> <br>The focus of this work was on the investigation of the properties of poly(methacrylic acid) (PMAA) brushes, a weak polyelectrolyte whose charge density can be tuned by adjustment of external parameters such as the solution pH-value. The PMAA brushes were swollen in aqueous solutions of different ionic composition and their properties were studied as a function of the valency, size (polarizability), concentration and nature of the ion. In another study, the complex formation of PMAA brushes with oppositely charged surfactants of different alkyl chain lengths was investigated. Stable complexes were formed with multivalent cations and oppositely charged surfactants. The complex formation behavior of PMAA brushes in contact with various small metal ion and oppositely charged surfactant solutions was investigated in detail, both, through in situ and ex situ measurements and significant new insights into the complex formation mechanism in such systems could be obtained. In particular, it was shown that already trace concentrations of certain ions and surfactants are sufficient to strongly alter the conformation of surface-attached molecules. This results in a strong modification of the layer properties such as the accessibility of functional groups. On the other side, seemingly small variations in the chemical details, such as interchanging the two divalent cations magnesium and copper which have the same charge and similar ionic radii, can have tremendous effects on the way these ions affect the polyelectrolyte brush structure. Moreover, these systems do not always behave as one would intuitively expect. For instance, the influence of monovalent silver ions on the weak polyacid brush structure is much closer related to that of divalent calcium ions than to that of monovalent sodium ions. <br> <br>These findings have important implications for the fundamental understanding of biological processes such as signaling, bioadhesion or the stabilization of micelles as in many biological systems (surface) biopolymers adopt constrained conformations similar to those of polymer brushes and a mix of different ions is usually present. Moreover, an understanding of the influence of certain ions on the molecular structure of thin surface-bound polyelectrolyte brushes is crucial for technological applications such as the electrosteric stabilization of colloids, the preparation of surfaces with ultra low friction properties or for the development of novel materials for drug delivery, biosensor or nanoreactor applications which rely on the fact that many proteins bind to such systems under preservation of their natural structure.","abstract_has_math":false,"creators":["Konradi, Rupert"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Rühe, Jürgen"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T02:22:22Z","subjects":["Polymerbürste","Polyelektrolytbürste","Polymethacrylsäure","Quellverhalten","Kation","polyelectrolyte","brush","swelling","radical polymerization","cation"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://freidok.uni-freiburg.de/data/1687","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Rühe, Jürgen"]},{"key":"dc:creator","label":"Author","values":["Konradi, Rupert"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["DoctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Polymerbürste","Polyelektrolytbürste","Polymethacrylsäure","Quellverhalten","Kation","polyelectrolyte","brush","swelling","radical polymerization","cation"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In this work, densely end-grafted polymer monolayers, so-called \"polymer brushes\", were covalently attached to solid planar surfaces and investigated with respect to their properties in contact with aqueous solutions of varying composition.
The synthesis of these polymer brushes was performed in two steps. First, an end-functionalized azoinitiator was covalently anchored to silicon wafers and planar glass substrates to form a self-assembled monolayer. Then, a surface-initiated free radical polymerization of vinyl monomers was triggered by thermal cleavage of the initiator (\"grafting from\" polymerization). By varying the monomer concentration and the polymerization time, the molecular weight of the surface-attached polymer chains and the anchoring density, a characteristic parameter that determines the degree of chain stretching of a polymer brush, could be reproducibly adjusted. Furthermore, different photopatterning strategies were implemented into the concept of surface-initiated polymerization. Using different approaches, positive and negative images of a mask and, in particular, laterally chemically microstructured polymer brushes could be obtained.
The focus of this work was on the investigation of the properties of poly(methacrylic acid) (PMAA) brushes, a weak polyelectrolyte whose charge density can be tuned by adjustment of external parameters such as the solution pH-value. The PMAA brushes were swollen in aqueous solutions of different ionic composition and their properties were studied as a function of the valency, size (polarizability), concentration and nature of the ion. In another study, the complex formation of PMAA brushes with oppositely charged surfactants of different alkyl chain lengths was investigated. Stable complexes were formed with multivalent cations and oppositely charged surfactants. The complex formation behavior of PMAA brushes in contact with various small metal ion and oppositely charged surfactant solutions was investigated in detail, both, through in situ and ex situ measurements and significant new insights into the complex formation mechanism in such systems could be obtained. In particular, it was shown that already trace concentrations of certain ions and surfactants are sufficient to strongly alter the conformation of surface-attached molecules. This results in a strong modification of the layer properties such as the accessibility of functional groups. On the other side, seemingly small variations in the chemical details, such as interchanging the two divalent cations magnesium and copper which have the same charge and similar ionic radii, can have tremendous effects on the way these ions affect the polyelectrolyte brush structure. Moreover, these systems do not always behave as one would intuitively expect. For instance, the influence of monovalent silver ions on the weak polyacid brush structure is much closer related to that of divalent calcium ions than to that of monovalent sodium ions.
These findings have important implications for the fundamental understanding of biological processes such as signaling, bioadhesion or the stabilization of micelles as in many biological systems (surface) biopolymers adopt constrained conformations similar to those of polymer brushes and a mix of different ions is usually present. Moreover, an understanding of the influence of certain ions on the molecular structure of thin surface-bound polyelectrolyte brushes is crucial for technological applications such as the electrosteric stabilization of colloids, the preparation of surfaces with ultra low friction properties or for the development of novel materials for drug delivery, biosensor or nanoreactor applications which rely on the fact that many proteins bind to such systems under preservation of their natural structure.","In der vorliegenden Arbeit wurden terminal dicht gepfropfte Polymermonolagen, sogenannte \"Polymerbürsten\", kovalent auf planaren Festkörperoberflächen verankert und hinsichtlich ihrer Eigenschaften in Kontakt mit wässrigen Lösungen verschiedener Zusammensetzung untersucht.
Die Darstellung der Polymerbürsten erfolgte in einer Zweistufensynthese. Zunächst wurde ein endfunktionalisierter Azoinitiator kovalent auf Siliziumwafern oder planaren Glassubstraten unter Ausbildung einer Initiatormonolage verankert. Dann wurde in einem zweiten Schritt eine freie radikalische Oberflächenpolymerisation durch thermisch induzierte Spaltung des Initiators gestartet. Dabei konnten das Molekulargewicht der oberflächenverankerten Ketten und der Abstand einzelner Verankerungspunkte gezielt und reproduzierbar durch Variation von Monomerkonzentration und Polymerisationszeit eingestellt werden. Insbesondere der Ankerabstand ist ein für Polymerbürsten charakteristischer Parameter, der den Grad der Streckung der oberflächengebundenen Ketten bestimmt. Das Konzept der oberflächengebundenen Polymerisation wurde desweiteren mit verschiedenen Strategien zur Photomikrostrukturierung kombiniert. In verschiedenen Verfahren konnten positive und negative Abbilder einer Maske und insbesondere auch lateral chemisch mikrostrukturierte Polymerbürsten erhalten werden.
Der Schwerpunkt dieser Arbeit lag auf der Untersuchung der Eigenschaften von Polymethacrylsäurebürsten (PMAA Bürsten). Polymethacrylsäure ist ein schwacher Polyelektrolyt, dessen Ladungsdichte eine Funktion der äußeren Bedingungen ist und z. B. über den pH-Wert in Lösung eingestellt werden kann. Die PMAA Bürsten wurden mit wässrigen Lösungen verschiedener Salze äquilibriert und ihre Eigenschaften in Abhängigkeit der Valenz, Größe (Polarisierbarkeit), Konzentration und Art des jeweiligen Ions untersucht. In einer weiteren Studie wurde die Komplexbildung von PMAA Bürsten mit gegensätzlich geladenen Seifenmolekülen unterschiedlicher Alkylkettenlänge untersucht. Mit mehrwertigen Ionen und gegensätzlich geladenen Seifen bildeten sich stabile Komplexe. Das Komplexbildungsverhalten von PMAA Bürsten in Kontakt mit Lösungen verschiedenster Metallionen und gegensätzlich geladener Seifen wurde detailliert sowohl durch in situ als auch durch ex situ Messungen untersucht. Dadurch konnten signifikante neue Einblicke in den Mechanismus der Komplexbildung solcher Systeme erhalten werden. Im Besonderen wurde gezeigt, dass bestimmte Ionen und Seifen bereits im Spurenkonzentrationsbereich erhebliche Änderungen in der Konformation der schichtbildenden Moleküle bewirken. Hieraus ergeben sich dann starke Änderungen in den Eigenschaften der Schichten, wie z. B. der Zugänglichkeit von funktionellen Gruppen. Andererseits zeigen die Untersuchungen aber auch, dass dabei die genauen chemischen Details eine entscheidende Rolle spielen. Beispielsweise unterscheiden sich die beiden zweiwertigen Ionen Magnesium und Kupfer trotz gleicher Ladung und ähnlicher Ionengröße sehr stark in ihrem Einfluss auf die Polyelektrolytbürstenstruktur. Weiterhin ist es wichtig zu beachten, dass sich diese Systeme nicht immer so verhalten, wie man intuitiv erwarten würde. So verhält sich zum Beispiel eine Polysäurebürste in Gegenwart von Silberionen ähnlich wie in Gegenwart von Kalziumionen, dieses Verhalten unterschiedet sich aber deutlich von dem in Gegenwart anderer einwertiger Ionen wie Natrium.
In vielen biologischen Systemen nehmen oberflächengebundene, geladene Biopolymere eine gestreckte Konformation ähnlich der von Polymerbürsten ein. Da in solchen Systemen außerdem üblicherweise verschiedenartige Ionen gegenwärtig sind, haben die Ergebnisse der hier vorgestellten Untersuchungen wichtige Konsequenzen für das Verständnis biologischer Prozesse wie der Signalgebung, der Bioadhäsion oder der elektrosterischen Stabilisierung von Mizellen. Weiterhin ist ein Verständnis des Einflusses bestimmter Ionen auf die molekulare Struktur ultradünner Polyelektrolytschichten von entscheidender Bedeutung für praktische Anwendungen wie der elektrosterischen Stabilisierung von Kolloiden, der Herstellung von Oberflächen mit extrem geringen Reibungskoeffizienten oder für die Entwicklung neuartiger Materialien die darauf beruhen, dass viele Proteine an Polyelektrolytbürstenmodifizierte Oberflächen unter Erhalt ihrer natürlichen Struktur binden. Mögliche Anwendungsfelder liegen hier im Bereich der gezielten Wirkstofffreisetzung, der Biosensoren oder von Nanoreaktoren auf Enzymbasis."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Weak polyacid brushes : synthesis, swelling behavior, complex formation and micropatterning","Bürsten schwacher Polysäuren : Synthese, Quellverhalten, Komplexbildung und Mikrostrukturierung"]}]}],"canonical_facts":{"dc:contributor":["Rühe, Jürgen"],"dc:creator":["Konradi, Rupert"],"dc:description.abstract":["In this work, densely end-grafted polymer monolayers, so-called \"polymer brushes\", were covalently attached to solid planar surfaces and investigated with respect to their properties in contact with aqueous solutions of varying composition.
The synthesis of these polymer brushes was performed in two steps. First, an end-functionalized azoinitiator was covalently anchored to silicon wafers and planar glass substrates to form a self-assembled monolayer. Then, a surface-initiated free radical polymerization of vinyl monomers was triggered by thermal cleavage of the initiator (\"grafting from\" polymerization). By varying the monomer concentration and the polymerization time, the molecular weight of the surface-attached polymer chains and the anchoring density, a characteristic parameter that determines the degree of chain stretching of a polymer brush, could be reproducibly adjusted. Furthermore, different photopatterning strategies were implemented into the concept of surface-initiated polymerization. Using different approaches, positive and negative images of a mask and, in particular, laterally chemically microstructured polymer brushes could be obtained.
The focus of this work was on the investigation of the properties of poly(methacrylic acid) (PMAA) brushes, a weak polyelectrolyte whose charge density can be tuned by adjustment of external parameters such as the solution pH-value. The PMAA brushes were swollen in aqueous solutions of different ionic composition and their properties were studied as a function of the valency, size (polarizability), concentration and nature of the ion. In another study, the complex formation of PMAA brushes with oppositely charged surfactants of different alkyl chain lengths was investigated. Stable complexes were formed with multivalent cations and oppositely charged surfactants. The complex formation behavior of PMAA brushes in contact with various small metal ion and oppositely charged surfactant solutions was investigated in detail, both, through in situ and ex situ measurements and significant new insights into the complex formation mechanism in such systems could be obtained. In particular, it was shown that already trace concentrations of certain ions and surfactants are sufficient to strongly alter the conformation of surface-attached molecules. This results in a strong modification of the layer properties such as the accessibility of functional groups. On the other side, seemingly small variations in the chemical details, such as interchanging the two divalent cations magnesium and copper which have the same charge and similar ionic radii, can have tremendous effects on the way these ions affect the polyelectrolyte brush structure. Moreover, these systems do not always behave as one would intuitively expect. For instance, the influence of monovalent silver ions on the weak polyacid brush structure is much closer related to that of divalent calcium ions than to that of monovalent sodium ions.
These findings have important implications for the fundamental understanding of biological processes such as signaling, bioadhesion or the stabilization of micelles as in many biological systems (surface) biopolymers adopt constrained conformations similar to those of polymer brushes and a mix of different ions is usually present. Moreover, an understanding of the influence of certain ions on the molecular structure of thin surface-bound polyelectrolyte brushes is crucial for technological applications such as the electrosteric stabilization of colloids, the preparation of surfaces with ultra low friction properties or for the development of novel materials for drug delivery, biosensor or nanoreactor applications which rely on the fact that many proteins bind to such systems under preservation of their natural structure.","In der vorliegenden Arbeit wurden terminal dicht gepfropfte Polymermonolagen, sogenannte \"Polymerbürsten\", kovalent auf planaren Festkörperoberflächen verankert und hinsichtlich ihrer Eigenschaften in Kontakt mit wässrigen Lösungen verschiedener Zusammensetzung untersucht.
Die Darstellung der Polymerbürsten erfolgte in einer Zweistufensynthese. Zunächst wurde ein endfunktionalisierter Azoinitiator kovalent auf Siliziumwafern oder planaren Glassubstraten unter Ausbildung einer Initiatormonolage verankert. Dann wurde in einem zweiten Schritt eine freie radikalische Oberflächenpolymerisation durch thermisch induzierte Spaltung des Initiators gestartet. Dabei konnten das Molekulargewicht der oberflächenverankerten Ketten und der Abstand einzelner Verankerungspunkte gezielt und reproduzierbar durch Variation von Monomerkonzentration und Polymerisationszeit eingestellt werden. Insbesondere der Ankerabstand ist ein für Polymerbürsten charakteristischer Parameter, der den Grad der Streckung der oberflächengebundenen Ketten bestimmt. Das Konzept der oberflächengebundenen Polymerisation wurde desweiteren mit verschiedenen Strategien zur Photomikrostrukturierung kombiniert. In verschiedenen Verfahren konnten positive und negative Abbilder einer Maske und insbesondere auch lateral chemisch mikrostrukturierte Polymerbürsten erhalten werden.
Der Schwerpunkt dieser Arbeit lag auf der Untersuchung der Eigenschaften von Polymethacrylsäurebürsten (PMAA Bürsten). Polymethacrylsäure ist ein schwacher Polyelektrolyt, dessen Ladungsdichte eine Funktion der äußeren Bedingungen ist und z. B. über den pH-Wert in Lösung eingestellt werden kann. Die PMAA Bürsten wurden mit wässrigen Lösungen verschiedener Salze äquilibriert und ihre Eigenschaften in Abhängigkeit der Valenz, Größe (Polarisierbarkeit), Konzentration und Art des jeweiligen Ions untersucht. In einer weiteren Studie wurde die Komplexbildung von PMAA Bürsten mit gegensätzlich geladenen Seifenmolekülen unterschiedlicher Alkylkettenlänge untersucht. Mit mehrwertigen Ionen und gegensätzlich geladenen Seifen bildeten sich stabile Komplexe. Das Komplexbildungsverhalten von PMAA Bürsten in Kontakt mit Lösungen verschiedenster Metallionen und gegensätzlich geladener Seifen wurde detailliert sowohl durch in situ als auch durch ex situ Messungen untersucht. Dadurch konnten signifikante neue Einblicke in den Mechanismus der Komplexbildung solcher Systeme erhalten werden. Im Besonderen wurde gezeigt, dass bestimmte Ionen und Seifen bereits im Spurenkonzentrationsbereich erhebliche Änderungen in der Konformation der schichtbildenden Moleküle bewirken. Hieraus ergeben sich dann starke Änderungen in den Eigenschaften der Schichten, wie z. B. der Zugänglichkeit von funktionellen Gruppen. Andererseits zeigen die Untersuchungen aber auch, dass dabei die genauen chemischen Details eine entscheidende Rolle spielen. Beispielsweise unterscheiden sich die beiden zweiwertigen Ionen Magnesium und Kupfer trotz gleicher Ladung und ähnlicher Ionengröße sehr stark in ihrem Einfluss auf die Polyelektrolytbürstenstruktur. Weiterhin ist es wichtig zu beachten, dass sich diese Systeme nicht immer so verhalten, wie man intuitiv erwarten würde. So verhält sich zum Beispiel eine Polysäurebürste in Gegenwart von Silberionen ähnlich wie in Gegenwart von Kalziumionen, dieses Verhalten unterschiedet sich aber deutlich von dem in Gegenwart anderer einwertiger Ionen wie Natrium.
In vielen biologischen Systemen nehmen oberflächengebundene, geladene Biopolymere eine gestreckte Konformation ähnlich der von Polymerbürsten ein. Da in solchen Systemen außerdem üblicherweise verschiedenartige Ionen gegenwärtig sind, haben die Ergebnisse der hier vorgestellten Untersuchungen wichtige Konsequenzen für das Verständnis biologischer Prozesse wie der Signalgebung, der Bioadhäsion oder der elektrosterischen Stabilisierung von Mizellen. Weiterhin ist ein Verständnis des Einflusses bestimmter Ionen auf die molekulare Struktur ultradünner Polyelektrolytschichten von entscheidender Bedeutung für praktische Anwendungen wie der elektrosterischen Stabilisierung von Kolloiden, der Herstellung von Oberflächen mit extrem geringen Reibungskoeffizienten oder für die Entwicklung neuartiger Materialien die darauf beruhen, dass viele Proteine an Polyelektrolytbürstenmodifizierte Oberflächen unter Erhalt ihrer natürlichen Struktur binden. Mögliche Anwendungsfelder liegen hier im Bereich der gezielten Wirkstofffreisetzung, der Biosensoren oder von Nanoreaktoren auf Enzymbasis."],"dc:format.medium":["application/pdf"],"dc:subject":["Polymerbürste","Polyelektrolytbürste","Polymethacrylsäure","Quellverhalten","Kation","polyelectrolyte","brush","swelling","radical polymerization","cation"],"dc:title":["Weak polyacid brushes : synthesis, swelling behavior, complex formation and micropatterning","Bürsten schwacher Polysäuren : Synthese, Quellverhalten, Komplexbildung und Mikrostrukturierung"],"dc:type":["DoctoralThesis"]},"updated_at":"2026-07-24T02:22:22Z"}