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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Self-incompatible solvents with ionic groups / Selbstinkompatible Lösungsmittel mit ionischen Gruppen

Wang, Yana 28 February 2013 (has links) (PDF)
The concept of a self-incompatible solvent is introduced as a molecule composed of two parts (compound 1 and 2) with unfavourable interactions. A third compound will be readily dissolved in this solvent to diminish this unfavourable interaction by dilution. The more incompatible compounds 1 and 2 are, the stronger this behaviour is expected to be. In this work, ionic liquids comprising non-polar carbon chain and polar ionic group are chosen to serve as a model of self-incompatible solvent. The interactions parameters k of the ionic liquids with active ingredients are investigated to examine the effect of self-incompatibility of the ionic liquid molecule. On the other hand, phase separation between compounds 1 and 2 will reduce the positive effect of self-incompatibility. The tendency of phase separation is increasing with increasing size of the two compounds. Thus, if compounds 1 and 2 are blocks tied together into a block copolymer, one expects a decreasing ability of the block copolymer to dissolve an active ingredient with increasing block length. In this work the ability of polybutadiene-block-poly(2-vinylpyridine) (PB-b-P2VP) block copolymers to dissolve the model compound anthracene is investigated. As expected, the solubility indeed decreases with increasing block length.
12

Partiell geschützte Blockcopolymere zur Darstellung von Polymerfilmen mit strukturierbarer und modifizierbarer Morphologie

Messerschmidt, Martin 01 December 2006 (has links) (PDF)
Gemäß der Zielstellung der Dissertation wurden verschiedene partiell tert.-Butyl- (TBU) und tert.-Butyloxycarbonyl- (Boc) geschützte Blockcopolymere auf der Basis von Poly(4-hydroxystyrol) mit engen Molmassenverteilungen sowie mit verschiedenen Blockzusammensetzungen dargestellt. Die Synthese dieser partiell TBU- und Boc-geschützten Blockcopolymere umfasste drei wesentliche Schritte: 1) Darstellung von Makroinitiatoren mittels NMRP, 2) Synthese von orthogonal geschützten Precursor-Blockcopolymeren durch Reinitiierung der Makroinitiatoren in Gegenwart eines weiteren orthogonal geschützten Monomeren und 3) orthogonale und quantitative polymeranaloge Umsetzungen ausgehend von den orthogonal geschützten Precursor-Blockcopolymeren. Mit den partiell TBU- und Boc-geschützten Blockcopolymeren wurden dünne Polymerfilme mittels „dip-coating“ präpariert. Die Untersuchung der Topographie und Morphologie der Filme erfolgte mit dem AFM. Aus den erhaltenen Topographie- und Phasenverschiebungsbildern ging eindeutig hervor, dass die verschiedenen Blöcke der jeweiligen partiell TBU- und Boc-geschützten Blockcopolymere in allen Polymerfilmen phasensepariert vorlagen. Reguläre Mikrostrukturen konnten allerdings nur bei den Polymerfilmen erhalten werden, deren Blockcopolymere sich allesamt durch asymmetrische Blockzusammensetzungen auszeichnen. Auf der Grundlage des statistischen Modellpolymeren Poly(styrol-r-4-hydroxystyrol) konnte ferner gezeigt werden, dass sich die phenolischen Hydroxylgruppen durch die Umsetzung mit Propargylbromid quantitativ in Propargylether-Gruppen umwandeln lassen und diese dann ihrerseits mit Hilfe der Cu(I)-katalysierten 1,3-dipolaren Cycloaddition (Click-Chemie) weiter mit einer Reihe von verschiedenen Aziden funktionalisiert werden können.
13

Synthesis of α-olefin-based copolymers and nanocomposites

Zakrzewska, Sabina 14 April 2015 (has links)
The research goal of this work was dedicated to improvement of the properties and enhancement of the application potential of commodity polymer based on polyolefins by choosing different synthesis routes to create new structures and materials. More precisely, the presented study explores different aspects of metallocene and post-metallocene catalyzed olefin polymerization leading to synthesis of novel copolymers and nanocomposites. The first part of this thesis deals with controlled polymerization of α-olefins catalyzed by post-metallocenes. Bis(phenoxyamine) zirconium complexes with [ONNO]-type ligands bearing cumyl (bPA-c) and 1-adamantyl (bPA-a) ortho-substituents were applied. For the polymerization catalyzed by bPA catalyst quasi-living kinetic character is proposed. The bPA catalyst was applied for synthesis of block copolymers by employing the strategy of sequential monomer addition. The blocky structure of the copolymer was successfully achieved and confirmed by NMR techniques. Moreover, the monomodal distribution of molar mass in SEC chromatogram confirmed the absence of homopolymers. In the second part of the work new defined comb-like copolymers (CLC) having a poly(10-undecene-1-ol) (PUol) backbone and densely grafted poly(ε-caprolactone) (PCL) side chains are presented. These copolymers were synthesized in two steps by means of metallocene polymerization followed by ring opening polymerization. Copolymers with varied and adjustable graft length (PCL segments) were synthesized. It was proved that the melting and crystallization temperatures of the CLC correlate with the PCL side chain length, i.e. longer chains result in higher Tm and Tc,o values. The melting enthalpy was found to be asymptotically dependent on the length of PCL side chains. The bulk morphology of the comb-like copolymers is proposed to be lamellar as judged from the TEM micrographs. The third part of the thesis is focused on the synthesis of polypropylene nanocomposites via in situ polymerization. Thereby, organomodified aluminumphosphate with kanemite-type layered structure (AlPO-kan) has been used as novel filler. Melt compounding composites were prepared for comparison purposes to evaluate the influence of in situ synthesis on the dispersion quality of the filler in polymer matrix. Melt compounding of neat AlPO-kan with PP did not lead to formation of nanocomposites. TEM images show macro-composites with the lamellar solid remaining agglomerated. On the contrary, in situ polymerization of propene yielded materials with exfoliated nanocomposite morphology. In XRD, diffractions of the AlPO-kan pilling of layers are not detectable. It can be concluded that the primary existing layers are delaminated. Very fine distribution of the filler in the polypropylene matrix has been impressively demonstrated by TEM.
14

Facile synthesis of bowl-shaped nitrogen-doped carbon hollow particles templated by block copolymer “kippah vesicles” for high performance supercapacitors

Lin, Zhixing, Tian, Hao, Xu, Fugui, Yang, Xiangwen, Mai, Yiyong, Feng, Xinliang January 2016 (has links)
This paper reports a simple self-assembly strategy towards bowl-shaped carbon-containing hollow particles, as well as an unprecedented potential application for block copolymer vesicles in energy storage. Kippah vesicles (fully collapsed vesicles), formed by solution self-assembly of an amphiphilic polystyrene-block-poly(ethylene oxide) block copolymer, were employed as the template to guide the formation of bowl-shaped nitrogen-doped carbon hollow particles (BNCHPs). As electrode materials of supercapacitors, BNCHPs exhibit superior electrochemical performance. In particular, compared with their spherical counterpart, BNCHPs largely increase their volumetric packing density, leading to much higher volumetric capacitance or volume reduction of electrodes, which is desired for practical supercapacitor devices.
15

Partiell geschützte Blockcopolymere zur Darstellung von Polymerfilmen mit strukturierbarer und modifizierbarer Morphologie

Messerschmidt, Martin 19 October 2006 (has links)
Gemäß der Zielstellung der Dissertation wurden verschiedene partiell tert.-Butyl- (TBU) und tert.-Butyloxycarbonyl- (Boc) geschützte Blockcopolymere auf der Basis von Poly(4-hydroxystyrol) mit engen Molmassenverteilungen sowie mit verschiedenen Blockzusammensetzungen dargestellt. Die Synthese dieser partiell TBU- und Boc-geschützten Blockcopolymere umfasste drei wesentliche Schritte: 1) Darstellung von Makroinitiatoren mittels NMRP, 2) Synthese von orthogonal geschützten Precursor-Blockcopolymeren durch Reinitiierung der Makroinitiatoren in Gegenwart eines weiteren orthogonal geschützten Monomeren und 3) orthogonale und quantitative polymeranaloge Umsetzungen ausgehend von den orthogonal geschützten Precursor-Blockcopolymeren. Mit den partiell TBU- und Boc-geschützten Blockcopolymeren wurden dünne Polymerfilme mittels „dip-coating“ präpariert. Die Untersuchung der Topographie und Morphologie der Filme erfolgte mit dem AFM. Aus den erhaltenen Topographie- und Phasenverschiebungsbildern ging eindeutig hervor, dass die verschiedenen Blöcke der jeweiligen partiell TBU- und Boc-geschützten Blockcopolymere in allen Polymerfilmen phasensepariert vorlagen. Reguläre Mikrostrukturen konnten allerdings nur bei den Polymerfilmen erhalten werden, deren Blockcopolymere sich allesamt durch asymmetrische Blockzusammensetzungen auszeichnen. Auf der Grundlage des statistischen Modellpolymeren Poly(styrol-r-4-hydroxystyrol) konnte ferner gezeigt werden, dass sich die phenolischen Hydroxylgruppen durch die Umsetzung mit Propargylbromid quantitativ in Propargylether-Gruppen umwandeln lassen und diese dann ihrerseits mit Hilfe der Cu(I)-katalysierten 1,3-dipolaren Cycloaddition (Click-Chemie) weiter mit einer Reihe von verschiedenen Aziden funktionalisiert werden können.
16

Multiphase coexistence with sequence fractionation in random block copolymers / Multi-Phasenkoexistenz mit Sequenz-Fraktionierung in statistischen Block-Copolymeren

von der Heydt, Alice 23 September 2011 (has links)
No description available.
17

Self-incompatible solvents with ionic groups

Wang, Yana 25 February 2013 (has links)
The concept of a self-incompatible solvent is introduced as a molecule composed of two parts (compound 1 and 2) with unfavourable interactions. A third compound will be readily dissolved in this solvent to diminish this unfavourable interaction by dilution. The more incompatible compounds 1 and 2 are, the stronger this behaviour is expected to be. In this work, ionic liquids comprising non-polar carbon chain and polar ionic group are chosen to serve as a model of self-incompatible solvent. The interactions parameters k of the ionic liquids with active ingredients are investigated to examine the effect of self-incompatibility of the ionic liquid molecule. On the other hand, phase separation between compounds 1 and 2 will reduce the positive effect of self-incompatibility. The tendency of phase separation is increasing with increasing size of the two compounds. Thus, if compounds 1 and 2 are blocks tied together into a block copolymer, one expects a decreasing ability of the block copolymer to dissolve an active ingredient with increasing block length. In this work the ability of polybutadiene-block-poly(2-vinylpyridine) (PB-b-P2VP) block copolymers to dissolve the model compound anthracene is investigated. As expected, the solubility indeed decreases with increasing block length.

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