Dokument: Cyclodextrins as Core Molecule in Supramolecular Assemblies and as Molecular Reinforcers in Polymer Coatings
| Titel: | Cyclodextrins as Core Molecule in Supramolecular Assemblies and as Molecular Reinforcers in Polymer Coatings | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=11521 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20090615-143639-0 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Sarvothaman, Mahesh Kumar [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Dr. h.c. Ritter, Helmut [Gutachter] PD Dr. Schaper, Klaus [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 540 Chemie | |||||||
| Beschreibung: | ABSTRACT
The inventions performed and discussed in this thesis relate in its entirety on cyclodextrins and cyclodextrin related compounds. Along the whole study, all the efforts were put in trying to exploit enormous opportunities that this biomolecule offers with synthetic chemistry. Cyclodextrin-mediated polymerization of hydrophobic monomers, owing to the well-documented ability of the CDs to form inclusion complexes, in aqueous solutions has been exploited in this work. Physicallylinked molecular structures namely, rotaxanes, opens a new window for polymer scientists in terms of polymer topology. As molecular composites, polyrotaxanes have indeed become an active field of research. This research also involves the development of mechanically interlocked polymer networks that incorporate CDs as one of their (ring) components. Difunctional acrylate and methacrylate monomers are complexed with CDs and polymerized in water leading to crosslinking systems incorporating CD. The discriminating influence of two kinds of cyclodextrins, α and β on the complexation and polymerization of afore mentioned monomers are studied. The complexes are analyzed by means of 1H NMR, 2D ROESY spectroscopy and Job’s curves which clearly revealed the discriminating characteristics of the two hosts towards complex formation. The obvious possibility of the smaller α-CD to form solid complexes leads to molecular packing structures of CD complexes in crystals. The crystal packing is determined by X-ray spectral analysis. More confirmations into the formation of interlocked polyrotaxanes are gathered from more spectral and thermal characterization. Relative spectral shifts in IR and a vast difference in Tg values of the interlocked polyrotaxanes as compared to their respective control polymers are recorded. Taking steps further away from the conventional synthetic methodologies, this work has concentrated on utilizing microwave induced syntheses. An approach is to obtain new classes of both linear and branched polyrotaxanes, incorporating microwave assisted synthesis. The ringopening polymerizations of ε-caprolactone in the vicinity of polymerizable cyclodextrins are monitored under microwave irradiation. A simultaneous ring-opening of the cyclic ester and a coupling reactions to the CD core is 6 observed, which results into the formation of a star polymer. GPC elugrams even revealed interesting insights into the formation of self-assemblies with time. Structure elucidations of the self-assemblies are performed by a competing complexation with adamantine as guest, which prevented any self-assembling by blocking the CD cavity. The effects of microwave energy into the formation of rotaxane and super structures by self-assembly is observed and are compared to similar reactions performed in conventional oil-baths. Trends in intrinsic viscosities of the star molecule and the supramolecule at precise intervals are recorded against reference poly(ε- caprolactone) that provided additional inputs into the entire reaction characteristics. Thermals analysis for each of the molecular species formed, served with influential confirmations. A total comparative study with respect to differently substituted CDs (hydroxypropyl and dimethyl) is carried out that provides a basis for understanding the mechanical and structural aspects of the supramolecules formed. A star polymer formation never occurred with the latter CDs, for many reasons, while an obvious complexation of the poly(ε-caprolactone) chains is evident with either of the alkyl substituted CDs. An associated work on cyclodextrins involves the construction of novel functional polymeric systems of CDs that can be covalently incorporated into a polymer matrix. In effect, such functionalized CDs can serve as reinforcement in polymeric materials, especially coatings. When polymerizable cyclodextrins (PCDs) are incorporated into a polymer chain, molecular interactions between the polymer matrix and the rigid CD molecule comes into play. During this study on molecular reinforcing properties of CD, a variety of CD derivatives are prepared and mixed on to different polymer binder systems. Appropriately functionalized CDs incorporated into a coating in specified amounts produced crosslinked products, anchoring the polymer chains intact. The high crosslink density of these polymers gives greater strength, durability and dimensional stability. Evaluation of these coatings regarding their elasticity, hardness, scratch and chemical resistance are compared. A CD incorporated polymer coating is found to exhibit appreciable overall performance, suggesting a perfect substitute to conventional reinforcing systems. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Chemie » Organische Chemie und Makromolekulare Chemie | |||||||
| Dokument erstellt am: | 15.06.2009 | |||||||
| Dateien geändert am: | 15.06.2009 | |||||||
| Promotionsantrag am: | 10.05.2009 | |||||||
| Datum der Promotion: | 15.06.2009 |
