Abstract not available

Abstract not available

Abstract: ABC triblock copolymers self-organize into a wide variety of supramolecular structures in the bulk. However, their associative behavior in selective solvents has scarcely been studied. Within the search for new stimuli-responsive supramolecular architectures, our attention focused on a pH-responsive polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) triblock copolymer. In addition to the synthesis of monodisperse spherical core-shell-corona (CSC) micelles, the reversibility and the cooperativity of the response to pH variations were studied, morphological transitions were induced and multi-responsive micellar gels were prepared. The micellization mechanism, the structure, the responsiveness and the internal organization of these new nanomaterials were investigated using a combination of transmission electronic microscopy, atomic force microscopy, light scattering, small-angle neutron and X-ray scattering, nuclear magnetic resonance and rheology. Finally, efforts were geared towards potential applications. The ability of PS-b-P2VP-b-PEO CSC micelles to encapsulate and release hydrophobic species was probed and gold nanoparticles were successfully synthesized within the P2VP layer of spherical and cylindrical micelles, which acted as nanoreactors./Résumé : Les copolymères triséquencés ABC sauto-organisent et forment une large gamme de structures supramoléculaires en phase solide. Cependant, peu détudes portent sur leur comportement associatif induit par des solvants sélectifs. Dans le cadre de la recherche de nouvelles architectures supramoléculaires sensibles aux stimuli externes, nous avons entrepris létude dun copolymère triséquencé sensible au pH : polystyrène-b-poly(2-vinylpyridine)-b-poly(oxyde déthylène). Outre la synthèse de micelles sphériques de type CSC, le caractère réversible et coopératif de la réponse au pH a été étudié, ainsi que linduction de transitions morphologiques et la préparation de gels micellaires sensibles à la température et au pH. Le mécanisme de micellisation, les paramètres structuraux, la sensibilité aux stimuli ainsi que lorganisation interne de ces nouveaux nanomatériaux ont été étudiés par une combinaison de microscopies électronique à transmission et à force atomique, diffusion lumineuse, diffusion de neutrons et rayons X aux petits angles, résonance magnétique nucléaire et rhéologie. Enfin, des applications ont été envisagées : la capacité des micelles CSC à encapsuler et libérer des composés hydrophobes a été testée et des nanoparticules dor ont été synthétisées avec succès au sein de ces nanoréacteurs, cest-à-dire dans la couche de P2VP des micelles sphériques et cylindriques.

Supramolecular chemistry covers intermolecular interactions where non-covalent bonds are involved, and many of them are based on host-guest interactions. Cyclodextrins (CDs) are cyclic oligosaccharides consisting of 6-, 7- or 8-glucose units, which are called alpha-, beta- or gamma-CDs, respectively. They have hydrophobic interior and hydrophilic exterior, and are widely being used as hosts for various organic molecules. The formation of CD inclusion complexes with a variety of dyes has continuously drawn our interests, since CDs are readily available and have ability to include dye molecules altering their properties. The present thesis covers the study of inclusion complexes of CDs and chromophore dyes, largely in two ways; rotaxane and pseudorotaxane. The stable rotaxane structure is achieved with the synthesis of dye rotaxane. The introduction of CD ring around azo chromophore provides a simple way to improve the solubility and stability of azo dye. We have shown that by incorporating proper compounds as a coupler, azo dye rotaxanes can be used as pH indicators and metal ion sensors. We have described the synthesis of novel acetylene dye rotaxane using the Pd-catalyzed reaction of Heck-Cassar-Sonogashira-Hagihara type. Its fluorescence properties in the solid state as well as in solutions are examined and compared with those of free dye. Free dye, which has tetra-carboxylic groups, is found to be highly sensitive to various metal ions, exhibiting high Stern-Volmer constants, K(SV). On the contrary, acetylene dye rotaxane exhibits much less quenching against various quenchers. The appearance of fluorescent anisotropic structure has been observed by the formation of inclusion complex between acetylene dye and gamma-CD. Its structural nature is studied by various techniques, including fluorescence, fluorescence anisotropy, wide angle X-ray scattering (WAXD) and differential scanning calorimetry (DSC) measurements. Methyl orange, an acid azo dye, forms a dimeric inclusion complex with gamma-CD, resulting in the formation stable anisotropic aggregates. Several other azo dyes are found to form anisotropic supramolecule in the presence of gamma-CD, and their structural characteristic has been discussed in terms of the number and position of solubilizing groups.

We have designed and synthesized a bistable pseudo-rotaxane carrying a fluorescent boradiazaindacene (BODIPY) unit. The intensity of the emission signal is dependent on the position of the cucurbituril (CB7) unit over the axle component. Thus, pH modulated switching of the CB7 wheel is accompanied by significant changes in the emission spectrum. Additionally, a thiosulfate-sulfite-iodate oscillating reaction which generates large amplitude pH oscillations can be carried out in the same solution. In such a solution, in response to changing pH, the position of the wheel component seems to change without outside intervention.

Supramolecular chemistry is an emerging field of chemistry which has attracted much attention in recent years as a result of its broad applicability in many areas. Thus, the design of functional supramolecular systems is strongly in demand in this field. For this purpose, we have developed near-IR emitting ratiometric fluorescent chemosensors for transition metal ions. Judicious placement of dithiodioxaazamacrocycles on the BODIPY chromophore generates this chemosensor which is selective for Hg(II) ions and both absorption and emission spectra display large changes that would allow ratiometric sensing.

Rational design of fluorescent chemosensors is an active area of supramolecular chemistry, photochemistry and photophysics. Ratiometric chemosensors are even more important, as they have an internal system for selfcalibration. In order to develop a new methodology for a ratiometric chemosensor design, we proposed coupling of energy transfer phenomenon to ion sensing. In this study, we targeted energy transfer cassette type chemosensors, where the efficiency of transfer is modulated on the donor side, by metal ion binding which changes the spectral overlap. This work involves the synthesis of a number of EET systems with varying degrees of EET efficiency. The results suggest that this strategy for ratiometric ion sensing is a promising one, enabling a modular approach in chemosensor design.

Supramolecular chemistry is an emerging field of chemistry which has attracted much attention in recent years as a result of its broad applicability in many areas. Thus, the design of functional supramolecular systems is strongly in demand in this field. For this purpose, we have developed novel phenylethynyl-BODIPY oligomer series which have absorption and emission maxima at the red part of the visible region of electromagnetic spectrum. Careful design to assemble the decyl groups to the system allowed us to dissolve the molecules in organic solvents easily. That`s why, not only we could characterize the molecules, but also spectroscopic and photopysical properties of them were investigated. As expected, as the number of repeating units &ldquo / n&rdquo / increase, peak absorption and emission wavelengths are shifted to the red end of the visible spectrum, with smaller increments as &ldquo / n&rdquo / increases. Consequently, these rigid rod like overall arrangement of oligomers could lead to applications as functional building blocks.

At present chemistry is undergoing an interesting change from the traditional preparation and investigation of single molecules to the construction and use of more complex functionalized architectures. Especially the better understanding of biological processes and the demand to create new materials with specific properties lead to a development of novel nanostructured assemblies that are held together by reversible weak interactions, that include coordination and hydrogen bonds, van der Waals forces as well as p-p and electrostatic interactions. Based on the smart use of Nature’s principles of molecular recognition and self-assembly, the supramolecular chemistry is now one of the pillars within the framework of nanotechnology. This contribution gives an overview on the basic concepts of supramolecular chemistry, the latter’s connections with biological systems and foreseeable applications. / Die Chemie erfährt gegenwärtig einen interessanten Übergang von der traditionellen Betrachtung der Einzelmoleküle hin zu großen komplexen Funktionseinheiten. Besonders das wachsende Verständnis biologischer Prozesse als auch die steigenden Forderungen nach neuen Werkstoffen mit einem spezifischen Eigenschaftsprofil führten zur gezielten Konstruktion definierter Baueinheiten auf der Nanometerskala. Dabei werden in intelligenter Weise reversible Bindungsprozesse auf Basis schwacher nichtkovalenter Wechselwirkungen, wie koordinative und Wasserstoffbrückenbindungen, Van-der-Waals- Kräfte sowie p−p- und elektrostatische Wechselwirkungen, genutzt. Aufbauend auf den natürlichen Prinzipien der molekularen Erkennung und Selbstorganisation ist die supramolekulare Chemie heute eine der Säulen in der Entwicklung der Nanotechnologie. Im Beitrag wird ein Überblick über wesentliche Aspekte der supramolekularen Chemie, ihre Anknüpfung an biologische Prinzipien und ausgewählte Nutzungsmöglichkeiten gegeben.

Title from PDF of title page. / Document formatted into pages; contains 80 pages. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The synthesis or the interaction between two or more molecules is known as supramolecular chemistry. The concept of supramolecular chemistry can be applied to the design of new pharmaceutical materials affording new compositions of matter with desirable composition, structure and properties. The design of a two-molecule, or binary, compound using complementary molecules represents an example of an application of crystal engineering. Crystal engineering is the understanding of intermolecular interactions, in the context of crystal packing, in the design of new solid materials. By identifying reliable connectors through molecular recognition or self-assembly, one can build predictable architectures. / ABSTRACT: The study of supramolecular synthesis was accomplished using known pharmaceutical molecules such as Nifedipine (calcium channel blocker used for cardiovascular diseases) and Phenytoin (used as an anticonvulsant drug) and model compounds containing synthons common in pharmaceutical drugs (Crown ethers and Trimesic acid with ether linkages and carboxylic acid dimers, respectively) with complementary molecular additives. The co-crystals formed were characterized by various techniques (IR, m.p., XPD, single X-ray diffraction) and preliminary results were found to exhibit characteristics different from the parent compounds as a direct result of hydrogen bonding and self-assembly interactions. These crystalline assemblies could afford improved solubility, dissolution rate, stability and bioavailability. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.