Convergent and divergent strategies for the synthesis of viologen dendrimers with 1,3,5-tri-methylene branching units are presented. The synthesis of 3,5-bis(hydroxymethyl) benzyl bromide was optimized. The analysis of the crystal structure of 1-[3,5-bis(hydroxymethyl)benzyl]-4-(pyridin-4-yl) pyridinium hexafluorophosphate together with PM3 calculations opens an avenue to judge the structure and conformation of benzylic viologen dendrimers. In order to study chemical trigger induced conformational changes, viologen dendrimers were spin-labeled via a divergent approach. 1-(2,4-dinitrophenyl)-4-(pyridin-4-yl)pyridinium hexafluorophosphate was used as the end group to yield an activated dendrimer of the respective generation. The corresponding dendrimers were spin-labeled by reacting the active functionality with 4-amino TEMPO. The products were characterized by ESR (spin-label efficiency) and conventional cyclic voltammetry. Dynamic ESR studies are planned. New trimethylene-dipyridinium dendrimers were synthesized via a divergent approach using 4-tert-butylbenzyl group as the peripheral group. These dendrimers are well soluble in DMF or DMSO as PF6 salts and they act as a host for anthraquinone-2,6-disulfonate (AQDS). They can be stoichiometrically titrated with AQDS as shown by 1H-NMR, DOSY and cyclic voltammetry. Upon loading them with AQDS, the dendrimers undergo first a contraction, they reach a minimum hydrodynamic radius for complete charge compensation and they re-open when overcharging takes place. The contraction is supported by MM+ calculations. Upon stepwise loading of G2 (42 positive charges) with AQDS (2 negative charges), the first 3 molar equivalents (6 neg. charges) occupy the innermost dendrimer shell (consisting of 6 pos. charges), the next 6 equivalents (12 neg. charges) occupy the middle shell (12 pos. charges) and the last 12 equivalents AQDS (24 neg. charges) occupy the outermost shell of the dendrimer (24 pos. charges), as supported by 1H-NMR titrations yielding the magic equivalent numbers of 3, 9=3+6, and 21=3+6+12. Such stepwise radial complexations again in DMSO were further demonstrated using other molecular guests (mono-, di- and trianionic) as well as with on purpose synthesized viologen dendrimers. α,ω-dibromoalkanes were bifunctionalized in two steps to yield alkyl phosphonates with pyridinium, trimethylenedipyridinium, bipyridinium or a sulfonate at their ω end. These compounds were used as surface modifiers to build biomimetic membranes on the pore walls of mesoporous TiO2. Host-guest interaction studies with on purpose synthesized viologen compounds have been performed in collaboration.

In der vorliegenden Arbeit wurden drei Klassen von Alkylen-verbrückten Viologendendrimeren hergestellt und im Hinblick auf einen möglichen Einsatz als Gentransfer-System untersucht. Diese drei Verbindungsklassen unterscheiden sich in den Alkylen-"Spacern" zwischen den Viologen-(4,4´-Bipyridinium)-einheiten. Es wurden Dendrimere mit Methylen-, Methylen / Hexamethylen- und Butylenspacern synthetisiert. Neben der benzylischen Starteinheit wurden auch zwei Dendrimere 0.ter Generation mit Porphyrinkern synthetisiert und eingesetzt. Die Verbindungen variierten im Durchmesser zwischen 3 und 9 nm, und in den Peripherieeinheiten, um eine eventuell vorhandene Größen- oder Endgruppenabhängigkeit zu bestimmen. Diese Viologendendrimere wurden mit zwei Plasmiden (5734 und 4731 Basenpaare) kombiniert und die gebildeten Dendriplexe mit vier Zelltypen auf eine Transfektionswirkung untersucht. Durch Variation des Inkubationsmediums, pH-Wert, Inkubationszeit und des Ladungsverhältnisses (-/ ) in den Transfektionsversuchen konnten Bedingungen gefunden werden die eine geringe Transfektion von zwei Zelltypen (CHO und PC 12) ergab. Um die Transfektionsbedingungen zu optimieren wurde die Dendriplexbildung zwischen Plasmid-DNA und Viologendendrimeren mit Agarosegelelektrophorese, Kraftmikroskopie, dynamische Lichtstreuung, Cyclovoltammetrie und Molecular Modeling untersucht. Die Ergebnisse der verschiedenen Methoden ließen sich miteinander korrelieren und konnten die Transfektionsergebnisse, z.B. durch den Nachweis notwendiger Dendriplexgrößen, untermauern.

Silicone release liners are silicone coatings on top of papers or films that are used in the adhesives industry to prevent adhesion before the final use of the adhesive e.g. labels. The process of production of release liners involves the casting of molten polysiloxanes on top of the substrates that crosslink by hydrosilylation reaction forming silicone networks. The quality of the release liner can be assessed by diverse methods usually performed when the coating process has been finished. Rarely an online control of the reaction is possible. Fluorescence spectroscopy was found to be a non-invasive useful method to control the reaction during the whole process by introducing very small concentration of fluorescent molecules in the polymer formulations; those fluorophores are sensitive to environmental changes as the silicone polymer molecules crosslink. In response to that stimulus, the fluorescence intensity varies along the time upon reaction allowing the identification of the gel point and further modifications or molecules rearrangements in a post-curing stage within weeks that are non-observable with conventional quality control methods. It was found that the fluorescent molecules do not require to be attached covalently to the polysiloxanes, thus fluorescence spectroscopy is a simple method to implement for controlling the production of silicone coatings. Moreover, the characterization of several silicone formulations was performed to find the optimal conditions for the production of release liners and to understand the effect of every component in the formulation on the performance of the silicones. The kinetics of the reaction was also studied and even a mechanism for the hydrosilylation reaction was proposed.

No description available.

This doctoral thesis focuses on synthesis of rigid star-shaped and rod-like viologen oligomers. The work is divided in two parts: synthesis, characterization and electropolymerization of star-shaped (i) and rod-like viologens oligomers (ii). In the first part the synthesis of viologen stars consisting of a phenyl core with triple 1,3,5-branching, each branch consisting of a linear alternating series of diphenyl (PhV++) and dibenzyl (BnV++) viologens and a variety of peripheral groups –X (Br, OH), is presented. A new electrochemical method of electrode modification (Gold, GC, ITO and CNTs) with viologen derivatives based on a benzyl radical coupling mechanism is described. The radicals are excessively generated at the star periphery resulting in a highly cross-linked polyviologen film with persisting star subunits. It is characterized by CV, STM and UV-Vis methods. Redox-titration experiments monitored by UV-Vis reveals that the reduction of the viologen stars begins at the periphery with the formation of PhV+•, continues with generation of BnV+• and ends with the reduction of the radical cations in the same sequence. Thus, viologen stars combine the unique redox and electrochromic property of isolated phenyl and benzyl viologen in one molecule. The second part of the thesis focuses on the step-wise synthesis of a library of rigid rod-like conjugated difunctional viologen/diphenyl oligomers with varying chain lengths including different side chain substitution. All oligomers are soluble in DMSO or MeOH depending on the counter anion (PF6- or Cl-). In order to tune the solubility of the oligomers, the side chains are tailored as methoxy, butoxy and oligo(ethylene oxide). The most solubilizing side-chains are of the oligo(ethylene oxide) type. All viologen oligomers are characterized by means of 1H-NMR, 13C-NMR, elemental analysis, optical spectroscopy and cyclic voltammetry. A simple surface functionalization and grafting technique has been developed for covalent binding of the viologen oligomers onto various conductive substrates e.g.: Au, GC and ITO. These modified electrodes are suitable for potential applications in designing field-effect transistors, sensors and supercapacitors. The polymer layers are characterized by means of FT-IR, STM, XPS and CV. The combined results presented in thesis represent a major advance in electrode functionalization by n-dopable viologen polymers and herald a variety of potential applications that make use of n-type semiconductors.

No description available.

Inhalt der Arbeit ist die Synthese und Charakterisierung von Hydrogelen auf Stärkebasis mit dem Ziel, diese für unterschiedliche Anwendungszwecke, insbesondere jedoch als Kontaktmedium in der medizinischen Ultraschalldiagnostik, einsetzen zu können. Um Stärke zur Ausbildung stabiler, wässriger Gele zu befähigen, werden mehrere Funktionalisierungsschritte vollzogen. Die Einführung von Carboxymethylfunktionen mittels Williamson-Reaktion erhöht den ionischen Charakter und damit die Hydrophilie des Biopolymers. Zur kinetischen Beschreibung der Carboxymethylierung am Stärkekorn in Suspension wird ein Dreiphasenmodell eingeführt. Der Aufbau eines für Gelstrukturen charakteristischen, dreidimensionalen Netzwerks erfolgt durch inter- und intramolekulare Verknüpfung einzelner Polymerstränge über kovalente Etherbrücken. Durch Eliminierung der nach Substitution und Vernetzung löslich verbliebenen Polymeranteile können die Materialeigenschaften des gequollenen Hydrogels erheblich verbessert werden. Rheologische Messungen und bildgebende Untersuchungen mit Gewebephantomen qualifizieren Stärke-Gele als in anwendungstechnischer Hinsicht geeignetes Kontaktmedium in der medizinischen Ultraschalldiagnostik. Mit speziellen Tests wird die pharmakologisch-toxikologische Unbedenklichkeit der Produkte nachgewiesen.