Techn. Universiẗat, Diss., 2004--Braunschweig.

<p>&nbsp / </p> <p align="left">The main aim of this study was to design new polyfunctional ligands based on the polypropyleneimine dendrimer&nbsp / <font face="Arial">DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 <font face="Arial">referred to as </font><b><font face="Arial,Bold">L1 </font><font face="Arial">in this work, to be used in </font></b></font></font><font face="Arial">copper mediated atom transfer radical polymerization (ATRP) of vinyl monomers. These ligands were synthesized by modifying DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 </font></font><font face="Arial">with aromatic and aliphatic substituents on the nitrogen atoms at the periphery of </font><b><font face="Arial,Bold">L1</font><font face="Arial">.</font></b></p>

<p>&nbsp / </p> <p align="left">The main aim of this study was to design new polyfunctional ligands based on the polypropyleneimine dendrimer&nbsp / <font face="Arial">DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 <font face="Arial">referred to as </font><b><font face="Arial,Bold">L1 </font><font face="Arial">in this work, to be used in </font></b></font></font><font face="Arial">copper mediated atom transfer radical polymerization (ATRP) of vinyl monomers. These ligands were synthesized by modifying DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 </font></font><font face="Arial">with aromatic and aliphatic substituents on the nitrogen atoms at the periphery of </font><b><font face="Arial,Bold">L1</font><font face="Arial">.</font></b></p>

No description available.

Philosophiae Doctor - PhD / A variety of nitrogen based dendritic ligands have been synthesized and used in copper mediated Atom Transfer Radical Polymerization (ATRP) of MMA. These ligands were derived from the commercially available Generation 1 polypropyleneimine dendrimer DAB-(NH2)4. The first set of ligands was synthesized by reacting DAB-(NH2)4 with aromatic aldehydes such as 2-pyridinecarboxyaldhyde and 4-t-butyl benzaldehyde to form imine functionalized dendrimers. Analogous secondary amine functionalized dendrimers were also synthesized by reducing the abovementioned imine functionalized dendrimers using sodium borohydride. The ligands produced were characterized by 13C / 1H NMR, and infra-red spectroscopy as well as elemental analysis to confirm its structure. The ligands were then used in copper mediated ATRP of MMA. The resulting polymer solutions were analyzed by Gas Chromatography (GC) to monitor the monomer conversion while the isolated polymers were analyzed by gel permeation chromatography (GPC) for molecular weight determination. Results showed that the primary and secondary amine and imine dendritic ligands were not efficient in promoting ATRP reactions. This led to the modification of DAB-(NH2)4 using methyl methacrylate to replace the peripheral amino groups of the DAB-(NH2)4 with tertiary amine groups. A second generation tertiary amine dendrimer was also synthesized in a similar fashion. The ligands obtained were then characterized using 13C and 1H NMR spectroscopy. The tertiary amine dendrimers were used in copper mediated ATRP of MMA. The polymerization medium was analyzed over time using GC to monitor monomer conversion while GPC was used for molecular weight determination of the resulting polymers. The results obtained using the methyl methacrylate modified ligands indicated that in the case of MMA polymerization, these ligands essentially conformed to the requirements of a good ATRP system. However in the preliminary studies, when employed in copper mediated ATRP of styrene, these ligands did not perform well. Further investigation is needed to improve the performance of these ligands in styrene polymerization under ATRP conditions. / South Africa

Aziridines are important building blocks for the synthesis of a wide range of organic compounds, including biologically active compounds and pharmaceuticals. The development of more cost-effective catalysts for atom transfer reactions is a continuing area of research in chemistry. Transition metal complexes have been shown to catalyze the aziridination of olefins, however, most require expensive metal ions or complex ligands. Meso-tetra(N-methyl-4-pyridyl)porphyrin (TMPyP4) is a highly charged, planar ligand that has been used to support manganese(III) in complexes like Mn[TMPyP4]I5. Herein we report the optimization of the reaction conditions for the aziridination of olefins in water and buffered solutions catalyzed by Mn[TMPyP4]I5. The reaction conditions optimized include pH range, temperature, and reaction time. Additionally, nitrogen sources, nitrogen source/olefin ratios, and catalyst loading were optimized. In buffered solutions, Mn[TMPyP4]I5 can effectively catalyze the generation of aziridines from various aromatic and aliphatic olefins with Chloramine T in moderate to good yields (43-93 %).

A new method for the synthesis of naphthalenes has been recently discovered. The Atom Transfer Radical Cyclisation (ATRC) of diverse 2-allylphenyl2',2',2'-trichloroacetates in the presence of a Cu complex afford schloronaphthalenes in good yields using either microwave or thermolytic methods of activation. A mechanism for the benzannulation reaction is proposed and experiments presented in order to validate this hypothesis. The use of 1,3-bis(2,6-diisopropylphenyl)imidazolium copper(I) chloride [(IPr)CuCl)] along with other metal carbenes is compared to the already reported CuCl/ligand system. Since the scope and synthetic utility of this new benzannulation reaction is restricted due to the use of the MW reactor, a solvent in which the thermal reaction can take place is reported, proving its efficiency in the synthesis of a range of substituted naphthalenes. The potential and versatility of the benzannulation reaction has been investigated. Studies towards the synthesis of gilvocarcin M which contains a tetracyclicaromatic core are presented. Gilvocarcins have potential use as anti-cancer agents and represent a member of the C-aryl glycosides found in natural products. Gilvocarcin M is a challenging target because there are a sparse number of total syntheses reported in the literature. The ATRC reaction of (vinyl)phenyl trichloroacetate has also been investigated, affording the synthesis of functionalised coumarins. The mechanism of this reaction has also been investigated, establishing that, in some cases, aretro-Kharasch reaction is observed.

In this thesis, acrylic polymers (methyl methacrylate, MMA; N,N' -dimethylamino ethyl methacrylate, DMAEMA; oligo-ethylene glycol methacrylate, OEGMA; trifluoroethyl methacrylate, TFEMA) were grafted from various metal surfaces such as cold rolled steel (CRS), stainless steel (SS), aluminum (Al) and nickel (Ni) through surface-initiated atom transfer radical polymerization (s-ATRP). The purpose is to improve corrosion resistance and to introduce multi-functionality to metal surface. The metal substrates were precisely polished and were facile for characterization by ellipsometry. 3-((alpha)-Bromo-2-methyl) propylamide propyltriethoxysilane was synthesized and immobilized on the metal surfaces under a simple and workplace-friendly condition. Grafting density was estimated to be 0.58 chains/nm^2 for CRS-gPMMA, 0.55 chains/nm^2 for Ni-g-PMMA and 0.18 chains/nm^2 for SS-g-DMAEMA and 0.66 chains/nm^2 for SS-g-PDMAEMA. Two strategies, i.e., "adding free initiator" and "adding deactivator", were adopted for the control over polymer molecular weight and grafting density in the CRS-g-PMMA system. The polymer thicknesses up to 80 nm were obtained within 80 min using the "adding deactivator" strategy. Copper and iron catalyst systems were compared on different metal substrates. A severe deactivation of copper catalyst was observed on the metal substrates. Controlled polymerization with relatively low polydispersity was obtained using the iron catalyst. The metal surfaces at various stages of modification were characterized by X-ray photoelectron spectroscopy, ellipsometry, goniometry, and atomic force microscopy (AFM). Electrochemical experiments were also carried out to measure the polarization resistance and corrosion potential of CRS-g-PMMA substrates. This thesis work demonstrated that the surface-initiated ATRP is a versatile means for the surface modification of metals with well-defined and functionalized polymer brushes. / Thesis / Master of Applied Science (MASc)

Substances that consist of nano-scale fillers dispersed in a polymer matrix are known as polymer-nanocomposites (PNCs). These materials are appealing since they have high potentials for applications, due to their mechanical, electrical, and thermo electrical properties. A common problem associated with PNCs is that the nano-fillers have a tendency to aggregate into clusters and form phase separated domains, which cause the desired properties of the system to either diminish or vanish all together. Hairy nanoparticles (HNPs) can avoid the issue of agglomeration that is commonly encountered by conventional PNCs. When polymer chains are grafted to a nanoparticle, and the coverage is high, the nanoparticles have decreased inter-particle interactions which allows for enhanced dispersion and mixing into a polymer matrix. By tailoring the architecture (functionalization of polymer chains, degree of polymerization, grafting density) of HNPs, it is possible to control the final properties of the system. An in depth study was carried out to investigate the effects of hairy-nanoparticle architecture on the resulting properties of the material itself. Atom transfer radical polymerization and living anionic polymerization were used to synthesize the polymer chains, of the HNP systems, while various instrumental methods including differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were utilized to study the physical ageing affects and self-assembly of these systems. #88ABW-2015-4971

We present a systematic methodology to functionalize magnetic nanoparticles through surface-initiated atom-transfer radical polymerization (ATRP). The magnetite nanoparticles are prepared according to the method proposed by Sun et al. (2004), which leads to a monodisperse population of ~ 6 nm particles stabilized by oleic acid. The functionalization of the nanoparticles has been performed by transforming particles into macro-initiators for the ATRP, and to achieve this two different routes have been explored. The first one is the ligand-exchange method, which consists of replacing some oleic acid molecules adsorbed on the particle surface with molecules that act as an initiator for ATRP. The second method consists in using the addition reaction of bromine to the oleic acid double bond, which turns the oleic acid itself into an initiator for the ATRP. We have then grown polymer brushes of a variety of acrylic polymers on the particles, including polyisopropylacrylamide and polyacrylic acid. The nanoparticles so functionalized are water soluble and show responsive behavior: either temperature responsive behavior when polyisopropylacrylamide is grown from the surface or PH responsive in the case of polyacrylic acid. This methodology has potential applications in the control of clustering of magnetic nanoparticles. / Singapore-MIT Alliance (SMA)