Interactions between the hydrological cycle and atmospheric chemistry

The land-atmosphere exchange of atmospheric trace gases is sensitive to meteorological conditions and climate change. It contributes in turn to the atmospheric radiative forcing through its effects on tropospheric chemistry. The interactions between the hydrological cycle and atmospheric processes are intricate and often involve different levels of feedbacks. The Earth system model EMAC is used in this thesis to assess the direct role of the land surface components of the terrestrial hydrological cycle in the emissions, deposition and transport of key trace gases that control tropospheric chemistry. It is also used to examine its indirect role in changing the tropospheric chemical composition through the feedbacks between the atmospheric and the terrestrial branches of the hydrological cycle. Selected features of the hydrological cycle in EMAC are evaluated using observations from different data sources. The interactions between precipitation and the water vapor column, from the atmospheric branch of the hydrological cycle, and evapotranspiration, from its terrestrial branch, are assessed specially for tropical regions. The impacts of changes in the land surface hydrology on surface exchanges and the oxidizing chemistry of the atmosphere are assessed through two sensitivity simulations. In the first, a new parametrization for rainfall interception in the densely vegetated areas in the tropics is implemented, and its effects are assessed. The second study involves the application of a soil moisture forcing that replaces the model calculated soil moisture. Both experiments have a large impact on the local hydrological cycle, dry deposition of soluble and insoluble gases, emissions of isoprene through changes in surface temperature and the Planetary Boundary Layer height. Additionally the soil moisture forcing causes changes in local vertical transport and large-scale circulation. The changes in trace gas exchanges affect the oxidation capacity of the atmosphere through changes in OH, O$_3$, NO$_x$ concentrations.

Polymer controlled mineralization of zinc phosphate hydrates and applications in corrosion protection, catalysis and biomedicine

ZUSAMMENFASSUNG Die Tauglichkeit von Hybridmaterialien auf der Basis von Zinkphosphathydrat-Zementen zum Einsatz als korrosionshemmende anorganische Pigmente oder zur prothetischen und konservierenden Knochen- und Zahntherapie wird weltweit empirisch seit den neunziger Jahren intensiv erforscht. In der vorliegenden Arbeit wurden zuerst Referenzproben, d.h. alpha-und beta-Hopeite (Abk. a-,b-ZPT) dank eines hydrothermalen Kristallisationsverfahrens in wässerigem Milieu bei 20°C und 90°C hergestellt. Die Kristallstruktur beider Polymorphe des Zinkphosphattetrahydrats Zn3(PO4)2  4 H2O wurde komplett bestimmt. Einkristall-strukturanalyse zeigt, daß der Hauptunterschied zwischen der alpha-und beta-Form des Zinkphosphattetrahydrats in zwei verschiedenen Anordnungen der Wasserstoffbrücken liegt. Die entsprechenden drei- und zweidimensionalen Anordnungen der Wasserstoffbrücken der a-und b-ZPT induzieren jeweils unterschiedliches thermisches Verhalten beim Aufwärmen. Während die alpha-Form ihr Kristallwasser in zwei definierten Stufen verliert, erzeugt die beta-Form instabile Dehydratationsprodukt. Dieses entspricht zwei unabhängigen, aber nebeneinander ablaufenden Dehydratationsmechanismen: (i) bei niedrigen Heizraten einen zweidimensionalen Johnson-Mehl-Avrami (JMA) Mechanismus auf der (011) Ebene, der einerseits bevorzugt an Kristallkanten stattfindet und anderseits von existierenden Kristalldefekten auf Oberflächen gesteuert wird; (ii) bei hohen Heizraten einem zweidimensionalen Diffusionsmechanismus (D2), der zuerst auf der (101) Ebene und dann auf der (110) Ebene erfolgt. Durch die Betrachtung der ZPT Dehydratation als irreversibele heterogene Festkörperstufenreaktion wurde dank eines „ähnlichen Endprodukt“-Protokolls das Dehydratationsphasendiagramm aufgestellt. Es beschreibt die möglichen Zusammenhänge zwischen den verschiedenen Hydratationszuständen und weist auf die Existenz eines Übergangszustandes um 170°C (d.h. Reaktion b-ZPT  a-ZPT) hin. Daneben wurde auch ein gezieltes chemisches Ätzverfahren mit verdünnten H3PO4- und NH3 Lösungen angewendet, um die ersten Stufe des Herauslösens von Zinkphosphat genau zu untersuchen. Allerdings zeigen alpha- und beta-Hopeite charakteristische hexagonale und kubische Ätzgruben, die sich unter kristallographischer Kontrolle verbreitern. Eine zuverlässige Beschreibung der Oberfächenchemie und Topologie konnte nur durch AFM und FFM Experimente erfolgen. Gleichzeitig konnte in dieser Weise die Oberflächendefektdichte und-verteilung und die Volumenauflösungsrate von a-ZPT und b-ZPT bestimmt werden. Auf einem zweiten Weg wurde eine innovative Strategie zur Herstellung von basischen Zinkphosphatpigmenten erster und zweiter Generation (d.h. NaZnPO4  1H2O und Na2ZnPO4(OH)  2H2O) mit dem Einsatz von einerseits oberflächenmodifizierten Polystyrolatices (z.B. produziert durch ein Miniemulsionspolymerisationsverfahren) und anderseits von Dendrimeren auf der Basis von Polyamidoamid (PAMAM) beschritten. Die erhaltene Zeolithstruktur (ZPO) hat in Abhängigkeit von steigendem Natrium und Wassergehalt unterschiedliche kontrollierte Morphologie: hexagonal, würfelförmig, herzförmig, sechsarmige Sterne, lanzettenförmige Dendrite, usw. Zur quantitativen Evaluierung des Polymereinbaus in der Kristallstruktur wurden carboxylierte fluoreszenzmarkierte Latices eingesetzt. Es zeigt sich, daß Polymeradditive nicht nur das Wachstum bis zu 8 µm.min-1 reduzierten. Trotzdem scheint es auch als starker Nukleationsbeschleuniger zu wirken. Dank der Koordinationschemie (d.h. Bildung eines sechszentrigen Komplexes L-COO-Zn-PO4*H2O mit Ligandenaustausch) konnten zwei einfache Mechanismen zur Wirkung von Latexpartikeln bei der ZPO Kristallisation aufgezeigt werden: (i) ein Intrakorona- und (ii) ein Extrakorona-Keimbildungsmechanismus. Weiterhin wurde die Effizienz eines Kurzzeit- und Langzeitkorrosionschutzes durch maßgeschneiderte ZPO/ZPT Pigmente und kontrollierte Freisetzung von Phosphationen in zwei Näherungen des Auslösungsgleichgewichts abgeschätzt: (i) durch eine Auswaschungs-methode (thermodynamischer Prozess) und (ii) durch eine pH-Impulsmethode (kinetischer Prozess. Besonders deutlich wird der Ausflösungs-Fällungsmechanismus (d.h. der Metamorphismus). Die wesentliche Rolle den Natriumionen bei der Korrosionshemmung wird durch ein passendes zusammensetzungsabhängiges Auflösungsmodell (ZAAM) beschrieben, das mit dem Befund des Salzsprühteste und der Feuchtigkeitskammertests konsistent ist. Schließlich zeigt diese Arbeit das herausragende Potential funktionalisierter Latices (Polymer) bei der kontrollierten Mineralisation zur Herstellung maßgeschneiderter Zinkphosphat Materialien. Solche Hybridmaterialien werden dringend in der Entwicklung umweltfreundlicher Korrosionsschutzpigmente sowie in der Dentalmedizin benötigt.

Structure, organization and dynamics of functional supramolecular materials studied by solid-state NMR

Functional materials have great importance due to their many important applications. The characterization of supramolecular architectures which are held together by non-covalent interactions is of most importance to understand their properties. Solid-state NMR methods have recently been proven to be able to unravel such structure-property relations with the help of fast magic-angle spinning and advanced pulse sequences. The aim of the current work is to understand the structure and dynamics of functional supramolecular materials which are potentially important for fuel-cell (proton conducting membrane materials) and solar-cell or plastic-electronic applications (photo-reactive aromatic materials). In particular, hydrogen-bonding networks, local proton mobility, molecular packing arrangements, and local dynamics will be studied by the use of advanced solid-state NMR methods. The first class of materials studied in this work is proton conducting polymers which also form hydrogen-bonding network. Different materials, which are prepared for high 1H conduction by different approaches are studied: PAA-P4VP, PVPA-ABPBI, Tz5Si, and Triazole-functional systems. The materials are examples of the following major groups; - Homopolymers with specific functional groups (Triazole functional polysiloxanes). - Acid-base polymer blends approach (PAA-P4VP, PVPA-ABPBI). - Acid-base copolymer approach (Triazole-PVPA). - Acid doped polymers (Triazole functional polymer doped with H3PO4). Perylenebisimide (PBI) derivatives, a second type of important functional supramolecular materials with potent applications in plastic electronics, were also investigated by means of solid-state NMR. The preparation of conducting nanoscopic fibers based on the self-assembling functional units is an appealing aim as they may be incorporated in molecular electronic devices. In this category, perylene derivatives have attracted great attention due to their high charge carrier mobility. A detailed knowledge about their supramolecular structure and molecular dynamics is crucial for the understanding of their electronic properties. The aim is to understand the structure, dynamics and packing arrangements which lead to high electron conductivity in PBI derivatives.

Petrogenetic evolution of Uralian-Alaskan-type mafic-ultramafic complexes in the southern and middle Urals, Russia

The PhD thesis at hand consists of three parts and describes the petrogenetic evolution of Uralian-Alaskan-type mafic ultramafic complexes in the Ural Mountains, Russia. Uralian-Alaskan-type mafic-ultramafic complexes are recognized as a distinct class of intrusions. Characteristic petrologic features are the concentric zonation of a central dunite body grading outward into wehrlite, clinopyroxenite and gabbro, the absence of orthopyroxene and frequently occurring platinum group element (PGE) mineralization. In addition, the presence of ferric iron-rich spinel discriminates Uralian-Alaskan-type complexes from most other mafic ultramafic rock assemblages. The studied Uralian-Alaskan-type complexes (Nizhnii Tagil, Kytlym and Svetley Bor) belong to the southern part of a 900 km long, N–S-trending chain of similar intrusions between the Main Uralian Fault to the west and the Serov-Mauk Fault to the east. The first chapter of this thesis studies the evolution of the ultramafic rocks tracing the compositional variations of rock forming and accessory minerals. The comparison of the chemical composition of olivine, clinopyroxene and chromian spinel from the Urals with data from other localities indicates that they are unique intrusions having a characteristic spinel and clinopyroxene chemistry. Laser ablation-ICPMS (LA-ICPMS ) analyses of trace element concentrations in clinopyroxene are used to calculate the composition of their parental melt which is characterized by enriched LREE (0.5-5.2 prim. mantle) and other highly incompatible elements (U, Th, Ba, Rb) relative to the HREE (0.25-2.0 prim. mantle). A subduction-related geotectonic setting is indicated by a positive anomaly for Sr and negative anomalies for Ti, Zr and Hf. The mineral compositions monitor the evolution of the parental magmas and decipher differences between the studied complexes. In addition, the observed variation in LREE/HREE (for example La/Lu = 2-24) can be best explained with the model of an episodically replenished and erupted open magma chamber system with the extensive fractionation of olivine, spinel and clinopyroxene. The data also show that ankaramites in a subduction-related geotectonic setting could represent parental magmas of Uralian-Alaskan-type complexes. The second chapter of the thesis discusses the chemical variation of major and trace elements in rock-forming minerals of the mafic rocks. Electron microprobe and LA-ICPMS analyses are used to quantitatively describe the petrogenetic relationship between the different gabbroic lithologies and their genetic link to the ultramafic rocks. The composition of clinopyroxene identifies the presence of melts with different trace element abundances on the scale of a thin section and suggests the presence of open system crustal magma chambers. Even on a regional scale the large variation of trace element concentrations and ratios in clinopyroxene (e.g. La/Lu = 3-55) is best explained by the interaction of at least two fundamentally different magma types at various stages of fractionation. This requires the existence of a complex magma chamber system fed with multiple pulses of magmas from at least two different coeval sources in a subduction-related environment. One source produces silica saturated Island arc tholeiitic melts. The second source produces silica undersaturated, ultra-calcic, alkaline melts. Taken these data collectively, the mixing of the two different parental magmas is the dominant petrogenetic process explaining the observed chemical variations. The results further imply that this is an intrinsic feature of Uralian-Alaskan-type complexes and probably of many similar mafic-ultramafic complexes world-wide. In the third chapter of this thesis the major element composition of homogeneous and exsolved spinel is used as a petrogenetic indicator. Homogeneous chromian spinel in dunites and wehrlites monitors the fractionation during the early stages of the magma chamber and the onset of clinopyroxene fractionation as well as the reaction of spinel with interstitial liquid. Exsolved spinel is present in mafic and ultramafic rocks from all three studied complexes. Its composition lies along a solvus curve which defines an equilibrium temperature of 600°C, given that spinel coexists with olivine. This temperature is considered to be close to the temperature of the host rocks into which the studied Uralian-Alaskan-type complexes intruded. The similarity of the exsolution temperatures in the different complexes over a distance of several hundred kilometres implies a regional tectonic event that terminated the exsolution process. This event is potentially associated with the final exhumation of the Uralian-Alaskan-type complexes along the Main Uralian Fault and the Serov-Mauk Fault in the Uralian fold belt.

Kinetic modeling and experiments on gas uptake and chemical transformation of organic aerosol in the atmosphere

Aerosolpartikel beeinflussen das Klima durch Streuung und Absorption von Strahlung sowie als Nukleations-Kerne für Wolkentröpfchen und Eiskristalle. Darüber hinaus haben Aerosole einen starken Einfluss auf die Luftverschmutzung und die öffentliche Gesundheit. Gas-Partikel-Wechselwirkunge sind wichtige Prozesse, weil sie die physikalischen und chemischen Eigenschaften von Aerosolen wie Toxizität, Reaktivität, Hygroskopizität und optische Eigenschaften beeinflussen. Durch einen Mangel an experimentellen Daten und universellen Modellformalismen sind jedoch die Mechanismen und die Kinetik der Gasaufnahme und der chemischen Transformation organischer Aerosolpartikel unzureichend erfasst. Sowohl die chemische Transformation als auch die negativen gesundheitlichen Auswirkungen von toxischen und allergenen Aerosolpartikeln, wie Ruß, polyzyklische aromatische Kohlenwasserstoffe (PAK) und Proteine, sind bislang nicht gut verstanden.rn Kinetische Fluss-Modelle für Aerosoloberflächen- und Partikelbulk-Chemie wurden auf Basis des Pöschl-Rudich-Ammann-Formalismus für Gas-Partikel-Wechselwirkungen entwickelt. Zunächst wurde das kinetische Doppelschicht-Oberflächenmodell K2-SURF entwickelt, welches den Abbau von PAK auf Aerosolpartikeln in Gegenwart von Ozon, Stickstoffdioxid, Wasserdampf, Hydroxyl- und Nitrat-Radikalen beschreibt. Kompetitive Adsorption und chemische Transformation der Oberfläche führen zu einer stark nicht-linearen Abhängigkeit der Ozon-Aufnahme bezüglich Gaszusammensetzung. Unter atmosphärischen Bedingungen reicht die chemische Lebensdauer von PAK von wenigen Minuten auf Ruß, über mehrere Stunden auf organischen und anorganischen Feststoffen bis hin zu Tagen auf flüssigen Partikeln. rn Anschließend wurde das kinetische Mehrschichtenmodell KM-SUB entwickelt um die chemische Transformation organischer Aerosolpartikel zu beschreiben. KM-SUB ist in der Lage, Transportprozesse und chemische Reaktionen an der Oberfläche und im Bulk von Aerosol-partikeln explizit aufzulösen. Es erforder im Gegensatz zu früheren Modellen keine vereinfachenden Annahmen über stationäre Zustände und radiale Durchmischung. In Kombination mit Literaturdaten und neuen experimentellen Ergebnissen wurde KM-SUB eingesetzt, um die Effekte von Grenzflächen- und Bulk-Transportprozessen auf die Ozonolyse und Nitrierung von Protein-Makromolekülen, Ölsäure, und verwandten organischen Ver¬bin-dungen aufzuklären. Die in dieser Studie entwickelten kinetischen Modelle sollen als Basis für die Entwicklung eines detaillierten Mechanismus für Aerosolchemie dienen sowie für das Herleiten von vereinfachten, jedoch realistischen Parametrisierungen für großskalige globale Atmosphären- und Klima-Modelle. rn Die in dieser Studie durchgeführten Experimente und Modellrechnungen liefern Beweise für die Bildung langlebiger reaktiver Sauerstoff-Intermediate (ROI) in der heterogenen Reaktion von Ozon mit Aerosolpartikeln. Die chemische Lebensdauer dieser Zwischenformen beträgt mehr als 100 s, deutlich länger als die Oberflächen-Verweilzeit von molekularem O3 (~10-9 s). Die ROIs erklären scheinbare Diskrepanzen zwischen früheren quantenmechanischen Berechnungen und kinetischen Experimenten. Sie spielen eine Schlüsselrolle in der chemischen Transformation sowie in den negativen Gesundheitseffekten von toxischen und allergenen Feinstaubkomponenten, wie Ruß, PAK und Proteine. ROIs sind vermutlich auch an der Zersetzung von Ozon auf mineralischem Staub und an der Bildung sowie am Wachstum von sekundären organischen Aerosolen beteiligt. Darüber hinaus bilden ROIs eine Verbindung zwischen atmosphärischen und biosphärischen Mehrphasenprozessen (chemische und biologische Alterung).rn Organische Verbindungen können als amorpher Feststoff oder in einem halbfesten Zustand vorliegen, der die Geschwindigkeit von heterogenen Reaktionenen und Mehrphasenprozessen in Aerosolen beeinflusst. Strömungsrohr-Experimente zeigen, dass die Ozonaufnahme und die oxidative Alterung von amorphen Proteinen durch Bulk-Diffusion kinetisch limitiert sind. Die reaktive Gasaufnahme zeigt eine deutliche Zunahme mit zunehmender Luftfeuchte, was durch eine Verringerung der Viskosität zu erklären ist, bedingt durch einen Phasenübergang der amorphen organischen Matrix von einem glasartigen zu einem halbfesten Zustand (feuchtigkeitsinduzierter Phasenübergang). Die chemische Lebensdauer reaktiver Verbindungen in organischen Partikeln kann von Sekunden bis zu Tagen ansteigen, da die Diffusionsrate in der halbfesten Phase bei niedriger Temperatur oder geringer Luftfeuchte um Größenordnungen absinken kann. Die Ergebnisse dieser Studie zeigen wie halbfeste Phasen die Auswirkung organischeer Aerosole auf Luftqualität, Gesundheit und Klima beeinflussen können. rn

Developments for transactinide chemistry experiments behind the gas-filled separator TASCA

Topic of this thesis is the development of experiments behind the gas-filled separator TASCA(TransActinide Separator and Chemistry Apparatus) to study the chemical properties of the transactinide elements.rnIn the first part of the thesis, the electrodepositions of short-lived isotopes of ruthenium and osmium on gold electrodes were studied as model experiments for hassium. From literature it is known that the deposition potential of single atoms differs significantly from the potential predicted by the Nernst equation. This shift of the potential depends on the adsorption enthalpy of therndeposited element on the electrode material. If the adsorption on the electrode-material is favoured over the adsorption on a surface made of the same element as the deposited atom, the electrode potential is shifted to higher potentials. This phenomenon is called underpotential deposition.rnPossibilities to automatize an electro chemistry experiment behind the gas-filled separator were explored for later studies with transactinide elements.rnThe second part of this thesis is about the in-situ synthesis of transition-metal-carbonyl complexes with nuclear reaction products. Fission products of uranium-235 and californium-249 were produced at the TRIGA Mainz reactor and thermalized in a carbon-monoxide containing atmosphere. The formed volatile metal-carbonyl complexes could be transported in a gas-stream.rnFurthermore, short-lived isotopes of tungsten, rhenium, osmium, and iridium were synthesised at the linear accelerator UNILAC at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The recoiling fusion products were separated from the primary beam and the transfer products in the gas-filled separator TASCA. The fusion products were stopped in the focal plane of TASCA in a recoil transfer chamber. This chamber contained a carbon-monoxide – helium gas mixture. The formed metal-carbonyl complexes could be transported in a gas stream to various experimental setups. All synthesised carbonyl complexes were identified by nuclear decay spectroscopy. Some complexes were studied with isothermal chromatography or thermochromatography methods. The chromatograms were compared with Monte Carlo Simulations to determine the adsorption enthalpyrnon silicon dioxide and on gold. These simulations based on existing codes, that were modified for the different geometries of the chromatography channels. All observed adsorption enthalpies (on silcon oxide as well as on gold) are typical for physisorption. Additionally, the thermalstability of some of the carbonyl complexes was studied. This showed that at temperatures above 200 °C therncomplexes start to decompose.rnIt was demonstrated that carbonyl-complex chemistry is a suitable method to study rutherfordium, dubnium, seaborgium, bohrium, hassium, and meitnerium. Until now, only very simple, thermally stable compounds have been synthesized in the gas-phase chemistry of the transactindes. With the synthesis of transactinide-carbonyl complexes a new compound class would be discovered. Transactinide chemistry would reach the border between inorganic and metallorganic chemistry.rnFurthermore, the in-situ synthesised carbonyl complexes would allow nuclear spectroscopy studies under low background conditions making use of chemically prepared samples.

Functionalization of hyperbranched polycarbosilanes - block copolymers and electrochemistry

Polycarbosilanes are a class of polymers at the interface between organic and inorganic chemistry. They are characterized by a high thermal and chemical inertness and high flexibility, especially pronounced for branched structures. Linear polycarbosilanes are well known as precursors for the preparation of SiCx ceramics. Additionally, more sophisticated architectures like dendrimers, hyperbranched polymers or block copolymers have been the subject of research for more than a decade. The scope of this work was to expand the properties and fields of application for polycarbosilane-containing structures. Thus, the work is divided in two major parts. The first part covers the synthesis and characterization of hyperbranched polycarbosilanes containing organometallic moieties. Hyperbranched poly-carbosilanes were synthesized using hydrosilylation of diallylmethylsilane and methyldiundecenylsilane. The degree of branching for polydiallymethylsilane was determined using standard 1H-NMR spectroscopy. The functional building blocks ferrocenyldimethylsilane and diferrocenylmethylsilane were synthesized which contain an isolated ferrocene unit or two ferrocenes bridged by silicon, respectively. Hyperbranched polycarbosilanes functionalized with ferrocenyl moieties were synthesized by modification of preformed polymers or by copolymerization of AB2 carbosilane monomers with AX-type ferrocenylsilanes. Polymers with Mn = 2500-9000g/mol and ferrocene contents of up to 67wt% were obtained. Electrochemical characterization by cyclic voltammetry revealed that polymers functionalized with isolated ferrocene units showed a single reversible oxidation wave, while voltammograms for polymers functionalized with diferrocenyl silane exhibited two well-separated reversible oxidation-reduction waves. This shows that the polymer bound ferrocenes bridged by silicon are electronically communicating and thus oxidation of the first ferrocene shifts the oxidation potential for the adjacent one. The polymers were utilized successfully for the preparation of modified electrodes with persistent and reproducible electrochemical response in organic solvents as well as in aqueous solution. The presented work has proven that ferrocenyl-functionalized hyperbranched polymers exhibit similar electrochemical properties as the analogous dendrimers. In a further approach it was shown that hyperbranched polymers containing organometallic moieties can be synthesized by polymerization of a new ferrocene-containing AB2 monomer - diallylferrocenylsilane. The second part of this work is dedicated to the preparation of core-functional hyperbranched polycarbosilanes. Low molecular weight ambifunctional molecules were synthesized that contain double bonds for the attachment of a polycarbosilane polymer as well as a second functionality available for further reaction and modification. Reactive vinyl groups in the core molecule allow an efficient attachment of hyperbranched polycarbosilane which was proven by MALDI-ToF and GPC. In combination with slow monomer addition techniques molecular weight and polydispersity of the polymers were controlled successfully. Core-functional polymers were characterized by NMR-spectroscopy, MALDI-ToF and GPC. Polymers with polydispersities <2 and molecular weights up to 5300g/mol were obtained. Transformation of the double bonds of the carbosilane was demonstrated with various silanes using hydrosilylation reaction or hydrogenation. Additionally, the core-functionality was varied resulting in polymers with bromo-, phthalimide-, amine- or azide moieties. Thus, a versatile synthetic strategy was developed that allows the synthesis of tailor-made polymers.A promising approach is the application of the polymer building blocks in copolymer synthesis. Bisglycidolization of amine-functional polycarbosilanes produces macro-initiators that are suitable for the multibranching-ring opening polymerization of glycidol. This experiments lead to the first example of hyperbranched-hyperbranched amphiphilic block copolymers, hb-PG-b-hb-PCS. Furthermore, the implementation of copper-catalyzed cycloaddition between azide-functional polycarbosilane and alkyne-functional poly(ethoxyethyl glycidylether) resulted in linear-hyperbranched block copolymers. The facile removal of acetal protecting groups provided convenient access to lin-PG-b-hb-PCS.

Multifunctional polyether architectures : versatile materials for surface attachment and functionalization

Chapter 1 of this thesis comprises a review of polyether polyamines, i.e., combinations of polyether scaffolds with polymers bearing multiple amino moieties. Focus is laid on controlled or living polymerization methods. Furthermore, fields in which the combination of cationic, complexing, and pH-sensitive properties of the polyamines and biocompatibility and water-solubility of polyethers promise enormous potential are presented. Applications include stimuli-responsive polymers with a lower critical solution temperature (LCST) and/or the ability to gel, preparation of shell cross-linked (SCL) micelles, gene transfection, and surface functionalization.rnIn Chapter 2, multiaminofunctional polyethers relying on the class of glycidyl amine comonomers for anionic ring-opening polymerization (AROP) are presented. In Chapter 2.1, N,N-diethyl glycidyl amine (DEGA) is introduced for copolymerization with ethylene oxide (EO). Copolymer microstructure is assessed using online 1H NMR kinetics, 13C NMR triad sequence analysis, and differential scanning calorimetry (DSC). The concurrent copolymerization of EO and DEGA is found to result in macromolecules with a gradient structure. The LCSTs of the resulting copolymers can be tailored by adjusting DEGA fraction or pH value of the environment. Quaternization of the amino moieties by methylation results in polyelectrolytes. Block copolymers are used for PEGylated gold nanoparticle formation. Chapter 2.2 deals with a glycidyl amine monomer with a removable protecting group at the amino moiety, for liberation of primary amines at the polyether backbone, which is N,N-diallyl glycidyl amine (DAGA). Its allyl groups are able to withstand the harsh basic conditions of AROP, but can be cleaved homogeneously after polymerization. Gradient as well as block copolymers poly(ethylene glycol)-PDAGA (PEG-PDAGA) are obtained. They are analyzed regarding their microstructure, LCST behavior, and cleavage of the protecting groups. rnChapter 3 describes applications of multi(amino)functional polyethers for functionalization of inorganic surfaces. In Chapter 3.1, they are combined with an acetal-protected catechol initiator, leading to well-defined PEG and heteromultifunctional PEG analogues. After deprotection, multifunctional PEG ligands capable of attaching to a variety of metal oxide surfaces are obtained. In a cooperative project with the Department of Inorganic and Analytical Chemistry, JGU Mainz, their potential is demonstrated on MnO nanoparticles, which are promising candidates as T1 contrast agents in magnetic resonance imaging. The MnO nanoparticles are solubilized in aqueous solution upon ligand exchange. In Chapter 3.2, a concept for passivation and functionalization of glass surfaces towards gold nanorods is developed. Quaternized mPEG-b-PqDEGA diblock copolymers are attached to negatively charged glass surfaces via the cationic PqDEGA blocks. The PEG blocks are able to suppress gold nanorod adsorption on the glass in the flow cell, analyzed by dark field microscopy.rnChapter 4 highlights a straightforward approach to poly(ethylene glycol) macrocycles. Starting from commercially available bishydroxy-PEG, cyclic polymers are available by perallylation and ring-closing metathesis in presence of Grubbs’ catalyst. Purification of cyclic PEG is carried out using α-cyclodextrin. This cyclic sugar derivative forms inclusion complexes with remaining unreacted linear PEG in aqueous solution. Simple filtration leads to pure macrocycles, as evidenced by SEC and MALDI-ToF mass spectrometry. Cyclic polymers from biocompatible precursors are interesting materials regarding their increased blood circulation time compared to their linear counterparts.rnIn the Appendix, A.1, a study of the temperature-dependent water-solubility of polyether copolymers is presented. Macroscopic cloud points, determined by turbidimetry, are compared with microscopic aggregation phenomena, monitored by continuous wave electron paramagnetic resonance (CW EPR) spectroscopy in presence of the amphiphilic spin probe and model drug (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO). These thermoresponsive polymers are promising candidates for molecular transport applications. The same techniques are applied in Chapter A.2 to explore the pH-dependence of the cloud points of PEG-PDEGA copolymers in further detail. It is shown that the introduction of amino moieties at the PEG backbone allows for precise manipulation of complex phase transition modes. In Chapter A.3, multi-hydroxyfunctional polysilanes are presented. They are obtained via copolymerization of the acetal-protected dichloro(isopropylidene glyceryl propyl ether)methylsilane monomer. The hydroxyl groups are liberated through acidic work-up, yielding versatile access to new multifunctional polysilanes.