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The phenolic resin chemistry is an old chemistry that started in the late 1800’s. A lot of research work to gain understanding of phenolic resins has been done and reported in literature. However, most of the studies are based on phenol novolac resins. It was necessary to acquire more knowledge on specifically o-cresol novolac (OCN) resins because of the interest in the production of these resins. The chemistry in question was new to Sasol and one of the major objectives of doing this work was to build in-house competency in this field. This was achieved by first investigating whether the available feed materials containing certain impurities can be used to synthesise o-cresol novolacs with set specifications of purity and physical characteristics. The suitability of the Sasol o-cresol in terms of its contamination with sulfur (which is sometimes found in relatively higher amounts due to operating conditions) was investigated. The results showed that the sulfur in o-cresol did not have a significant contribution in the sulfur of the OCN. Another contaminant, formic acid, an auto-oxidation product found in formalin solutions was also investigated. It was also observed that, at formic acid levels of up to 4000 ppm, there was no effect on the softening point of the OCN. Secondly, it was important to study and understand the effect of different reaction variables on the quality of the OCN resins. The effect of formaldehyde: o-cresol molar ratio was investigated, the softening point increased with the increase in the molar ratio. The effects of other reaction variables (catalyst, reaction time, temperature and formaldehyde feed rate) on the softening point of the OCN were also investigated using p-toluenesulfonic acid and oxalic acid as catalysts. With p-toluenesulfonic acid as a catalyst, the temperature had no effect on the softening point, while all the other variables showed an effect on this parameter. A softening point model was formulated, which predicted the softening point with 98% accuracy. With oxalic acid, only the amount of catalyst had an effect. In addition, the chemical structures of these compounds were studied using 13C-NMR spectroscopy. The focus was on the isomer distribution of the methylene linkages. / Prof. D.B.G. Williams

M.Sc. (Chemistry) / The objective of the project was the synthesis of thiosemicarbazone-triazole hybrid compounds and evaluation of their biological activities against malaria and obesity. In achieving our objective, compound 63 was synthesized from the reaction of benzaldehyde 62 with propargyl bromide. Click chemistry reaction of compound 63 with benzyl azide provided triazole 68. Schiff’s base condensation of triazole 68 with methyl hydrazine carbodithioate 67 furnished compound 69 which then underwent nucleophilic substitution reaction and afforded thiosemicarbazone-triazole hybrids 61a-j. The structures of the compounds were characterized using NMR spectroscopy and elemental analysis. Hybrids 61a-h were then investigated for their biological activities against malaria and obesity. The antimalarial activities of the hybrids against the 3D7 strain of the malaria parasite plasmodium falciparum showed that only hybrid 61f exhibited less than 50% parasite viability (46% compared to 37% of chloroquine). The dose response of the hybrids was not carried out due to their poor activities. Hybrids 70a-h that incorporated electron donating group in their aromatic linker were synthesized similarly as hybrids 61a-h were synthesized. Their antimalarial activities showed that all except 70c and 70g exhibited less than 50% parasite viability. The test results indicated that the addition of methoxy group to the hybrids 61b, 61e and 61f decreased their percentage parasite viability which were exhibited by their corresponding hybrids 70b, 70e and 70f, respectively. Hybrid 70f was found to be marginally active with a dose response of 7.09 μM. The anti-obesity and anti-diabetic effects of hybrids 61a-h were investigated against the mitochondrial genes (Acc-1, Cpt-1 and Pgc-1) and glucose transport genes (Glut-4, Mef2a and Nrf-1), respectively. The test results against the mitochondrial genes showed that hybrids 61e and 61h consistently exhibited on the 3 genes which indicated that the presence of a non-polar short branched chain of the amine moiety might be important in the up-regulation of oxidative (Cpt-1 and Pgc-1) and down regulation of lipid accumulation (Acc-1) genes. The test results on the glucose transport genes showed that 61e followed by 61f consistently exhibited on the 3 genes which indicated that the presence of a non-polar short branched chain of the amine moiety might be important in the up-regulation of Glut-4, Mef2a and Nrf-1.Hybrids 70a-h were also tested against obesity and type 2 diabetes mellitus. Their investigation on the mitochondrial genes showed that the addition of methoxy group to the hybrids 61a-h that have a non-polar long branched chain of the amine moiety could be a reason for the expression and suppression of Cpt-1, Pgc-1 and Acc-1, respectively. The test results of hybrids 70a-h on glucose transport genes showed that the addition of methoxy group to the hybrids 61a-h that have a non-polar short (straight and branched) alkyl chain of the amine moiety might be a reason for the up-regulation of Glut-4, Mef2a and Nrf-1. Carbohydrate incorporated thiosemicarbazone-triazole hybrid compound 75 was successfully synthesized. However, the synthesis of more libraries of compound 75 and investigation of their biological activities against malaria and obesity were not carried out due to time constraints.

M.Sc. / The prevalence of toxic contaminants in water remains a huge challenge for water supplying companies and municipalities. Both organic and inorganic contaminants (especially heavy metals) pollutants are often present in water distribution networks. Organic and inorganic pollutants often co-occur in drinking water networks. However, at present there is no water treatment intervention that simultaneously removes organic and inorganic pollutants from water. Additionally, current water treatment technologies fail to remove these contaminants to parts per billion (ppb or µg.L-1) levels. Methods that can simultaneously remove organic and inorganic pollutants to desired levels need to be developed. In our laboratories, both functionalised and unfunctionalised cyclodextrin (CD) polymers have demonstrated the ability to effectively remove organic species from water at low (ppb) concentrations. Cyclodextrins (CDs), which are cyclic oligomers consisting of glucopyranosyl units linked together through α-1,4-glycosidic linkages, behave like molecular hosts. They are capable of interacting with a range of guest molecules within their cylindrical hydrophobic cavities thereby forming the so-called inclusion complexes. Their solubility in water, however, precludes their application in the removal of organic pollutants from water. This limitation is easily dealt with by polymerizing the CDs into water insoluble polymers with suitable bifunctional linkers. On the other hand, ionic liquids (ILs) have been reported to “absorb” heavy metal ions from aqueous media. ILs are low melting point molten salts that are composed of organic cations (e.g. imidazolium and pyridinium ions) and mostly inorganic anions like Cl–, Br–, [PF6]– and [BF4]–. In this study, the two systems were combined by an initial attachment of the imidazolium or pyridinium rings to the cyclodextrin moiety. Polymerisation of the resulting cyclodextrin-ionic liquid (CD-IL) complexes with a suitable linker produced the corresponding water insoluble CD-IL polymers. This dual system has shown excellent capabilities for the removal of model pollutants such as p-nitrophenol (PNP) and 2,4,6-trichlorophenol (TCP) and chromium (Cr6+) from aqueous media. However, the CD-IL polymers showed very little affinity for the absorption of cadmium from water. TGA and DSC studies showed that these polymers are stable over a wide range of temperatures (100-400 C).

M.Sc. / Carbon nanotubes are among the most exciting new materials being investigated and synthesized, owing to their outstanding mechanical, electronic and optical properties. For more than a decade, the translation of these properties into realistic applications has been hindered by solubility and processing difficulties. Recently the development of efficient methodologies for covalent chemical modification has raised hope for the use of these materials in various fields of application such as biosensors, vaccine and drug delivery systems, medical imaging, biomaterials, water purification, etc... Phosphorylation of functionalized and unfunctionalized multiwalled carbon nanotubes (MWCNTs) is reported in this dissertation. This was achieved by the incorporation of phosphorus moieties on the end and side walls of the MWCNTs. Pristine MWCNTs were functionalized through oxidation by sodium hypochlorite and with a mixture of sulphuric and nitric acids, a diazonium coupling method and by reduction of amide functions on the surface of MWCNTs. Then condensation reactions with alkyl or aryl chlorophosphates were undertaken to obtain compounds 7 to 12. Phosphorylation of pristine MWCNTs was achieved by a 1, 3 dipolar cyclo addition of diphenyl phosphoryl azide. Characterization of the phosphorylated multiwalled carbon nanotubes has been performed by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy X-Ray Dispersive Spectroscopy (EXDS), Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared (FTIR) and Raman Spectroscopy. These techniques together gave evidence for surface, structure and chemical modifications of the synthesized material.

In 1896, Becquerel discovered the natural radioactivity in potassium uranyl sulphate. Since then, Pierre and Marie Curie, E. Rutherford and F. Soddy all made tremendous contributions to the discovery of many other radioactive elements. The work of all these scientists has shown that all elements found in nature with an atomic number greater than 83 (bismuth) are radioactive. Artificial radioactivity was first reported by I. Curie and F. Joliot in 1934. These scientists irradiated boron and aluminium targets with a particles from polonium and observed positrons emitted from the target even after removal of the a particle source. This discovery of induced or artificial radioactivity opened up a brand new field of tremendous importance. Around the same time, the discovery of the cyclotron, deuteron and neutron by various scientists facilitated the discovery of many more artificial radioactivities. At present time more than 2700 radionuclides have been produced artificially in the cyclotron, the nuclear reactor, the neutron generator and linear accelerator. Radiopharmaceuticals are drugs that contain a radionuclide and are used for imaging if the radionuclide is a photon emitter (gamma-g or positron-b+) or for therapy if the radionuclide is a particle emitter (alpha-a or beta-b- or Auger/conversion e-). / Prof. A. Roodt

The contamination of water by organic compounds has resulted in an escalation in research efforts to combat this problem. These organics can be harmful to human health and the environment in general, and they pose unique challenges to several industrial applications. Even when present at very low concentrations, they tend to bioaccumulate and interact with endocrine systems. However, due to the chemical nature of these compounds, current technologies are still challenged to effect their removal from water. Of currently used technologies, activated carbon and reverse osmosis can remove most of the organic pollutants but fail to remove them to very low concentrations (ng/L levels). Recent studies have explored the capabilities of nanoporous cyclodextrin (CD) polymers, a class of nanomaterials that show great potential to absorb organic contaminants from water. The project reported in this dissertation was undertaken to further explore the efficacy of these polymers in order to assist industries and municipalities in their quest to solve the problem of water contamination by organic species. The ability of these polymers to remove selected organic contaminants from water at varying concentrations was studied. The investigated pollutants were chlorinated disinfection by-products (DBPs), taste and odour causing compounds (geosmin and 2-methylisoborneol) and humic acid, which was used to mimic natural organic matter (NOM). Water samples were pre-concentrated using solid phase extraction (SPE) and subsequently quantified by Gas Chromatography-Mass Spectrometry (GC/MS). The CD polymers demonstrated absolute efficiency at quenching organics at very low concentrations compared to granular activated carbon (GAC). The recyclability efficiency of the CD polymers was also investigated. Most of the work was carried out using rapid small scale column tests (RSSCTs) that were designed in our laboratories. The general design of the study and pathway that was followed while conducting these experiments is shown in the flow diagram on the next page. / Dr. B.B. Mamba

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