<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>

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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

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.

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)

Many pathogenic bacteria can enter phagocytic cells and replicate in them, and these intracellular bacteria are difficult to treat because the recommended antibiotics do not transport into the cells efficiently. Examples include food-borne bacteria such as Salmonella and Listeria as well as more toxic bacteria such as Brucella and the Mycobacteria that lead to tuberculosis. Current treatments utilize aminoglycoside antibiotics that are polar and positively charged and such drugs do not enter the cells in sufficient concentrations to eradicate the intracellular infections. We have developed core-shell polymeric drug delivery vehicles containing gentamicin to potentially overcome this challenge. Pentablock and diblock copolymers comprised of amphiphilic nonionic polyether blocks and anionic poly(sodium acrylate) blocks have been complexed with the cationic aminoglycoside gentamicin. The electrostatic interaction between the anionic polyacrylates and the cationic aminoglycosides form the cores of the nanoplexes, while the amphiphilic nature of the polyethers stabilize their dispersion in physiological media. The amphiphilic nature of the polyethers in the outer shell aid in interaction of the nanoplexes with extra- and intra-cellular components and help to protect the electrostatic core from any physiological media. This thesis investigates the electrostatic cooperativity between the anionic polyacrylates and cationic aminoglycosides and evaluated the release rates of gentamicin as a function of pH. / Master of Science

1,8-bis(phenylimino)-3,6-ditertbutyl-carbazole is synthesized and characterized, which can be complexed with copper(II) halide by deprotonation and transmetallation. The resulting copper complexes enable to polymerize MMA through RATRP process.

The aim of this work was to successfully prepare polymers of N-(2-hydroxypropyl)methacrylamide, (PHPMA) using controlled/"living" free-radical polymerisation technique. For this purpose, atom transfer radical polymerisation (ATRP) and reversible addition-fragmentation (chain) transfer (RAFT) polymerisation were used in preparation of a number of base polymers with the intention of quantitatively converting them into PHPMA. Both methods were applied under varying polymerisation conditions, and the kinetics of the systems investigated. Various rate constants were measured, while computer modelling of the experimental data allowed estimation of other kinetic parameters of interest. Investigations into solvent and ligand effects on the kinetics of ATRP of the activated ester methacryloyloxy succinimide (MAOS) and one of the archetypal methacrylate monomers, methyl methacrylate (MMA) were carried out. The method of RAFT was also employed in polymerisation of MAOS and a number of other monomers in the hope of finding the best synthetic precursor of PHPMA. Polymers of methacryloyl chloride (MAC) and p-nitrophenyl methacrylate (NPMA) were prepared, as well as the polymers of HPMA itself and N-isopropyl methacrylamide. Polymerisation of MMA by RAFT was also attempted in view of adding to current knowledge on the monomer's behaviour and the kinetic characteristics of its RAFT polymerisation. Preparation of PHPMA from PMAOS, PMAC and PNPMA was attempted. Successful preparation of PHPMA from the polymer of the acid chloride was achieved under mild reaction conditions, while displacement of N-hydroxysuccinimide groups of PMAOS resulted in unexpected modification of the polymer under the conditions used. Conversion of PNPMA into PHPMA was not achieved. At this stage these results suggest inadequacy of both PMAOS and PNPMA as reactive polymeric precursors.