Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Please refer to full text for abstract

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / This thesis reports on an exploratory investigation of proposed sludge guideline limits of heavy metal (cadmium, chromium, copper, nickel, lead and zinc) concentrations for South Africa. The purpose of the study is to determine allowable heavy metal concentrations in sludge for use as fertilizer in agriculture that can be attained and is practically possible without being detrimental to the environment. This determination was done by investigating the potential sources and concentrations of these heavy metals at the Potsdam Wastewater Treatment Works (WWTW) and also the efficiency of the treatment works in removal of these heavy metals. A heavy metal mass balance of both the influent at the Potsdam WWTW and the wastewater through the treatment works was calculated. This study also proposes possible interventions to minimize the levels of these heavy metals. Results for the heavy metal mass balance of the influent showed that a large quantity of some metals were unaccounted for, this implies that either industries discharge illegally after hours or the present monitoring undertaken by the City of Cape Town is inadequate. The large percentage of unaccounted cadmium suggests another source, which should be further investigated. The mass balance of the wastewater through Potsdam WWTW concluded that all these heavy metal limits were attainable, and that in some cases can be lowered even more. The treatment works has a high removal efficiency of these heavy metals, and a substantial reduction of these limits is justified. In the period of this study, the area under investigation gradually expanded, as more industries were established in it. Although the works was performing beyond its capacity it nevertheless was able to attain the rigorous heavy metal limits in sludge that are envisaged. There has also been a reduction in limits of heavy metals for discharge of final effluent into waterbodies; this study shows that these limits are also attainable.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / This study comprises the preparation and characterisation of completely new Fischer-type carbene complexes of chromium and tungsten by deprotonation of (CO)5M=C(NMe2)(Me), (CO)5M=C(OMe)(Me) or (CO)5M=C(NMe2)C≡CH, and subsequent treatment of the formed anion with a variety of reagents, including reactive metal complexes. The deprotonation of the termodynamically stable complexes, (CO)5M=C(NMe2)(Me) (M = Cr or W) followed by reaction with the sulfonium salt, [Me2(MeS)S][BF4], yielded not only the expected products (CO)5M=C(NMe2)CH2SCH3, but also thioether complexes, (CO)5MS(CH3)2, disulfinated complexes (CO)5M=C(NMe2)CH(SCH3)2, S-bridged dinuclear compounds (CO)5M=C(NMe2)CH2S(CH3)M(CO)5, as well as the unique fourmembered- C,S-chelate carbene complexes (CO)4Cr=C(NMe2)CH(SCH3)SCH3 and (CO)4M=C(NMe2)CH2SCH3. Crystal structure determinations of (CO)5W=C(NMe2)CH(SCH3)2, (CO)5Cr=C(NMe2)CH2S(CH3)Cr(CO)5, (CO)4M=C(NMe2)CH2SCH3 (M = Cr, W) and (CO)4Cr=C(NMe2)CH(SCH3)SCH3 were successfully performed. The latter tetracarbonyl complexes have Cr-S bonding distances of 2.4531(9) and 2.4517(5) Å and a W-S distance of 2.577(1) Å. These relatively weak bonds contribute to the short M-C(O)-distances trans to it. The formed four membered chelate rings are essentially planar. The deprotonation of (CO)5Cr=C(NMe2)(Me) and sequential reaction with sulphur and CF3SO3Me does not yield the expected product, (CO)5Cr=C(NMe2)CH2SCH3, but (CO)5CrS=C(NMe2)CH3 resulting from a sulphur insertion was isolated. A single crystal structure determination of the latter complex shows a normal thione carbene complex. The reaction of methyl(methoxy)carbenepentacarbonylchromium(0) and the tungsten analogue with n-BuLi, followed by reaction with [Me2(MeS)S][BF4], afforded unexpected complexes via an unusual addition dissimilar to the above mentioned reactions of dimethylaminocarbene complexes. The formation of the products, (CO)5M=C(OMe)[CH=C(Me)NH(Me)] and (CO)4M=C(OMe)[C(SMe)=C(Me)NH(Me)] (M = Cr, W) can be ascribed to the influence of the heteroatom, oxygen, as well as the presence of acetonitrile in the sulfonium salt reagent [Me2(MeS)S][BF4]. An unusual alkylation by Me+ is also affected. The X-ray crystallographic structure determination of the complexes show hydrogen bonding between the alkoxy oxygen atoms and the protons on the nitrogen atoms. The latter four membered C,S-chelates show bonding distances and angles similar to these of the previously mentioned four membered chelates. Deprotonation of the alkynyl carbene complexes, (CO)5M=C(NMe2)C≡CH (M = Cr, W), with n-BuLi and subsequent reaction with PPh3AuX (X = Cl, NO3), initially afford the β-transmetalated products (CO)5M=C(NMe2)C≡CAuPPh3. In solution (CH2Cl2) the product isomerises through metal migration to Ph3PAuC(NMe2)=C=C=W(CO)5. The conversion was followed by means of 1H-NMR-spectroscopy and it appears that two first order reactions take place consecutively.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2008. / A method for the detection of adulteration of South African Sauvignon blanc wines, by enrichment with foreign sources of 3-alkyl-2-methoxypyrazenes, is described. The levels of three 3-alkyl-2-methoxypyrazenes (3-isobutyl-, 3- isopropyl- and 3-sec-butyl-2-methoxypyrazine) in South African Sauvignon blanc wines were measured with liquid chromatography-mass spectrometry. Sample preparation involved clean-up and pre-concentration by distillation followed by solvent extraction of the distillate with dichloromethane. Extracts were acidified and concentrated by evaporation and finally reconstituted to a fixed volume to affect quantitative pre-concentration of the samples. Sample extracts were separated with reversed phase liquid chromatography utilizing a phenyl-hexyl separation column. Residues were measured with liquid chromatography-mass spectrometry utilizing a tandem quadrupole mass spectrometric detector operated in multiple reaction monitoring mode for optimal trace level quantitation. Atmospheric pressure chemical ionization was utilized as electrospray ionization was found to suffer from quenching effects attributed to the sample matrix. Qualitative information was obtained from the relevant molecular ions as well as two secondary ion transitions (and one ion ratio) in each case. Recoveries obtained by the extraction procedure were better than 90% with coefficient of variance of better than 10% at concentrations from 1 to 100 ng/L. The limit of detection of the method was 0.03 ng/L and the limit of quantification 0.10 ng/L for the three analytes measured. The described LC-MS method is more sensitive for the determination of 3-alkyl-2-methoxypyrazines in wine than GC methods reported for the same purpose. From the experimental data, a set of parameters were established to discriminate adulterated South African Sauvignon blanc wines. It was demonstrated that the 3-isobutyl-2-methoxypyrazine concentration, despite showing considerable variance, was confined to a relatively narrow range spanning approximately two orders of magnitude (0.20 to 22 ng/L). A clear indication of possible maximum values for this compound in South African Sauvignon blanc wines was obtained from the analysis of a large number of samples (577), spanning most relevant wine producing regions and representing vintages 2003 to 2006. It was also demonstrated that South African Sauvignon blanc wines contain the major 3- alkyl-2-methoxypyrazenes in reasonably distinct relative amounts and that the said ratios of abundance may be used to elucidate authenticity. The expected effect of adulteration with green pepper extracts or some synthetic preparations on the 3-isobutyl-2-methoxypyrazine concentration as well as the relative abundances were also determined by characterizing the corresponding profiles in green peppers and some synthetic flavor preparations. Two adulterated samples in the dataset were identified by both outlined criteria. A limited number of wines of other cultivars were also analyzed. The results represent the most complete and accurate data on the 3-alkyl-2-methoxypyrazine content of South African Sauvignon blanc wines to date. A publication covering the work presented in this thesis is currently in preparation.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2008. / In this study, the coordination of certain Group 6 and Group 10 & 11 metals to Odonor and S-donor ligands were investigated. For the most part, this involved the isolation of new Mo(VI) and W(VI) complexes. By using a distribution diagram that shows the dependence of the type of species in solution with pH, we attempted to crystallize new polyoxoanion species of the two metals. It was found that the products that crystallize are not necessarily dependant upon the relative concentrations of the species in solution, but rather on the effective packing of the crystal types that are prepared. During this study a unique W(VI) polyanion, [(CH3CH2)4N]2[W6O19] (4), was isolated. The Mo(VI) analogue of this compound as well as the dinuclear Mo(VI)-W(VI) complex have been reported previously, but a pure W(VI) compound of this type has not been successfully isolated yet. A new polymorph of a known dimolybdate, K2Mo2O7·H2O (1), was also crystallized, even though dimolybdate species do not generally occur in solution. This structure, although previously reported, shows some differences with the one in the literature, in particular large deviations in unit cell dimensions. Subsequently, as a second component of this study, a variety of carboxylates were coordinated to Mo(VI) and W(VI) species in an acidic medium. Two new complexes of Mo(VI) with these carboxylate ligands were isolated: [(CH3CH2)4N][MoO3(mal)]·H2O (5) (mal = malate) and Na6[Mo2O5(cit)2] (6) (cit = citrate). The ligands are two- and threefold deprotonated respectively and coordinate in a polydentate manner to the metal centra. The formation of compound 5 in solution has been known for many years, but the structure of this complex has not been determined in the solid state until now. Also, the tungsten analogue of compound 6 was reported years ago, but the Mo(VI) complex has not been crystallized before. Compounds 5 and 6 exhibit a 1:1 and 2:2 metal to ligand ratio respectively, and these ratios are quite rare in Mo(VI) crystal chemistry. Finally, the dimolybdate complex, [CH3)3N(CH2)6N(CH3)3][Mo2O7(cit)] (7), was isolated, and its structure determined and compared to the one in the literature. In the third part of this study, our attention shifted to the group 10 and 11 metals, platinum and gold. Attempts were made to coordinate unusual ligands with donor atoms P, Se and/or S to these metal centers. During this investigation, we isolated a unique Pt(IV) complex, PtCl2(S3C8H7)2 (9). The structure of this compound that was determined crystallographically involves the coordination of two identical R-SCS2 fragments to the metal ion forming four-membered chelate rings. No compounds of Pt and Au with the P-Se ligand, P3Se3(C(C6H5)3)3, could be isolated. However, a mixed valence compound of Au(I,III), [Au(I)Cl(S(CH2C6H5)2)][Au(III)Cl3(S(CH2C6H5)2] (8), could be isolated and characterized. In this compound Au exhibits two oxidation states, +1 and +3. Although the complex has been reported previously, the structure was not described fully, and we now unequivocally determined its crystal structure. The extended structure shows the formation of chains of alternating Au(I) and Au(III) centers with a separation of 5.610 Å.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Co-crystals are excellent materials for studying intermolecular interactions in the solid-state and can be used to further our knowledge of the balance between strong and weak intermolecular interactions. The O–H∙∙∙∙∙∙Narom synthon was chosen as the focus of this investigation of hydrogen bonding motifs. The starting materials selected all have two hydrogen bond donor and/or acceptor sites for the formation of extended networks. All molecules are also aromatic such that the influence of weaker π∙∙∙∙∙∙π interactions can be included in the study. Two 3x3 grids of related co-crystals were produced from these starting materials and are reported in this thesis as part of an ongoing investigation into a broader set of co-crystals. A part of the work describes the investigation of co-crystals prepared by the combination of related benzenediol and diazine isomers taken from a 3x3 grid. The solid-state structures of each of the six starting materials are discussed briefly to describe the nature of intermolecular interactions involved in the single component crystals. Trends in hydrogen-bonding patterns as well as the weaker interactions identified in the starting materials, can be used to recognise those in the subsequent multi-component crystals. Thirteen co-crystal compounds were obtained, of which twelve structures are novel. Each of these co-crystal structures is discussed in terms of intermolecular interactions and packing in the solid state. Hydrogen-bonding patterns and structural similarities are highlighted in related co-crystal structures as well as between co-crystals and their respective starting materials. The combination of benzenediol isomers with benzodiazine isomers yielded seven novel co-crystal structures in a second 33 grid is reported. The structure of phthalazine, which has not yet been reported, is included in addition to these co-crystals, while the structures of quinazoline and quinoxaline that were retrieved from the CSD are discussed briefly. Co-crystal structures are discussed individually, focusing on the intermolecular interactions that are significant to the structural architecture of the compound. Certain co-crystals that display structural similarities with structures of the 3x3 grid, as well as with co-crystals presented in Chapter 3, are discussed in the relevant sections. Lastly, two extended pyridyl diyne ligands that were synthesised for use in future co-crystallisation studies similar to those reported earlier are briefly highlighted. The crystal structures of the pure compounds and of a hydrate of one of the ligands were obtained and discussed briefly. To date only one of these structures has been reported in the literature.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The number of coordination complexes utilizing bis-pyridyl diamide ligands has increased significantly over the past decade. This is attributed to the relatively easy synthetic procedure of the ligands and interesting structural features such as helicity, water clusters and porosity that the coordination complexes possess. In the first part of this study, the following eight structurally related bis-pyridyl diamide ligands: • N,N'-bis(pyridin-4-ylmethyl)isophthalamide (ISO); • N,N'-bis(pyridyl-4-ylmethyl)terephthalamide (TER); • N,N'-bis(pyridin-4-ylmethyl)hexanediamide (ADI); • N,N'-bis(pyridin-4-ylmethyl)butanediamide (SUC); • N,N'-bis(pyridin-4-ylmethyl)biphenyl-4,4'-dicarbonyl dicarboxamide (DIP); • N,N'-dipyridin-2-ylpentanediamide (GLUT); • (2E)-N,N'-bis(2-pyridin-4-ylmethyl)but-2-enediamide (FUM); • 4-(pyridin-4-ylmethyl)aminocarbonyl benzoic acid (TER-A). were synthesized and characterized by NMR, FTIR, MS and SCD. In the second part, the synthesized ligands were reacted with a variety of transition metal salts to yield fifteen novel coordination polymers and one discrete complex. SCD analysis showed that of the sixteen complexes thirteen formed 1-D chains, two formed 2-D networks, and one formed a discrete unit. Hydrogen bonding interactions between water molecules, the counterions and the amide groups resulted in connection of the lower dimension entities into higher dimension networks. The synthesized ligands were co-crystallized with trimesic acid and a novel co-crystal consisting of ADI and trimesic acid was obtained. SCD analysis showed that the co-crystal featured the amide homosynthon as well as the pyridine/carboxylic acid heterosynthon. / AFRIKAANSE OPSOMMING: Die aantal koördinasie komplekse met dipiridieldiamied ligande het noemenswaardig vermeerder oor die afgelope dekade. Hierdie groei kan toegeskryf word aan die eenvoudige sintetiese prosedure en interessante strukturele eienskappe van dié koördinasie komplekse, wat o.a. helikse, waterbondels en poreuse materiale vorm. In die eerste deel van hierdie studie is die agt onderstaande struktureel verwante dipiridieldiamied ligande se sintese en karakterisering deur kernmagnetieseresonansie, Fourier transform infrarooi, massaspektrometrie en enkel kristal X-straal diffraksie (SCD) beskryf: • N,N'-bis(piridien-4-ielmetiel)isoftalamied (ISO); • N,N'-bis(piridien-4-ielmetiel)tereftalamied (TER); • N,N'-bis(piridien-4-ielmetiel)heksaandiamied (ADI); • N,N'-bis(piridien-4-ielmetiel)butaandiamied (SUC); • N,N'-bis(piridien-4-ielmetiel)bifeniel-4,4'-dikarbonieldikarboksamied (DIP); • N,N'-dipiridien-2-ielpentaandiamied (GLUT); • (2E)-N,N'-bis(2-piridien-4-ielmetiel)but-2-eendiamied (FUM); • 4-(piridien-4-ielmetiel)aminokarboniel bensoësuur (TER-A). In die tweede gedeelte is bg. ligande met 'n reeks oorgangsmetaalsoute gereageer om vyftien nuwe koördinasiepolimere, asook een diskrete kompleks, te lewer. SCD analise toon dat van hierdie sestien komplekse vorm dertien 1-D kettings, twee vorm 2-D netwerke en slegs een vorm 'n diskrete eenheid. Waterstofbindings tussen die water molekules, die teen-ione en die amied groepe het laer dimensie (1-D) eenhede verbind om hoër dimensionele netwerke (2-D) te vorm. Mede-kristallisasie van die gesintetiseerde ligande met trimesielsuur het 'n nuwe mede-kristal tussen ADI en triemesielsuur opgelewer. Enkelkristal diffraksie toon dat die mede-kristal beide die amied homosinton en die piridien/karboksielsuur heterosinton bevat.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Resorcinarenes are macrocyclic products formed from the condensation of aldehydes (aliphatic or aromatic) and resorcinol and have been used in a wide range of applications since their first synthesis. Applications include: HPLC stationary phases for the separation of pyrimidine bases, racemic drugs and isomers, the selective extractions of lanthanides and actinides, as molecular receptors, catalysis, NMR chiral shift agents, GC separations and as starting materials for the synthesis of macrocyclic compounds (e.g. cavitands and carcerands) to name but a few. The use of resorcinarenes in catalysis is still quite new and unexplored, while catalysis using calix[4]arenes, a related macrocycle, has been widely studied. In this thesis it was attempted to synthesise a C2v symmetric resorcinarene precursor that could be further functionalised to form distal bidentate ligands for coordination to transition metals. These compounds would then ultimately be used in catalytic testing, especially for Pd catalysed C-C bond formation. A dibromo resorcinarene precursor was synthesised starting from resorcinarene, using methodology developed by Shivanyuk. This molecule was functionalised with a small range of different electrophiles using lithium halogen exchange methodology, although low yields were returned for the expected distal resorcinarene compounds. Other methods of functionalisation of the resorcinarene, using an anionic ortho-Fries rearrangement and the reduction of a dinitrile resorcinarene to amine and aldehyde functionalities proved unsuccessful. Using a dithioether resorcinarene a di-nuclear coordination compound was formed with Pd(II). This compound was tested for catalytic activity with a Heck reaction, showing low yields for the coupling of styrene with bromobenzene. / AFRIKAANSE OPSOMMING: Resorsinarene is makrosikliese produkte wat gevorm word deur die kondensasie van aldehiede (alifaties of aromaties) met resorsinol en word in ‘n verskeidenheid van toepassings gebruik sedert hulle eerste sintese. Tipiese voorbeelde sluit in: stationêre fases vir die HPLC-skeiding van pirimidien-basisse, rasemiese farmaseutiese middels en isomere, die selektiwe ekstraksie van lantaniede en aktiniede, molekulêre reseptore, katalise, chirale verskuiwingsreagense vir KMR spektrometrie, GC-skeidings en as uitgangverbindings vir die sintese van ander makrosikliese verbindings (bv. kavitande en karserande). Die gebruik van resorsinarene in katalise is ’n splinternuwe onontginde veld. In teenstelling hiermee is calix[4]areen, ’n verwante makrosikliese verbinding, baie meer bestudeer en vir katalise gebruik. Die doel van hierdie tesis was om ’n C2v simmetriese uitgangstof te sintetiseer wat verder gefunksionaliseer kan word om distale, bidentate ligande vir koordinasie met oorgangsmetale te lewer. Daar is beplan om die katalitiese eienskappe van die komplekse te toets, veral vir Pd-gekataliseerde C–C-koppelings reaksies. Deur gebruik te maak van ’n protokol wat deur Shivanyuk ontwikkel is, is ’n dibromo-resorsinareen gesintetiseer uit resorsinareen. Verskillende elektrofiele is in ’n litium-halogeen uitruilreaksie gebruik om ’n beperkte verskeidenheid nuwe ligande te sintetiseer wat verskillende funksionele groepe besit. Ongelukkig was die opbrengste aan distale ligande baie laag en ander metodes is dus ook ondersoek om die funksionalisering te bewerkstellig. ’n Anioniese orto-Fries herrangskikkingsreaksie en die reduksie van ’n dinitriel-resorsinareen om amien- en aldehiedfunksies te lewer, was ook onsuksesvol. Die reaksie tussen ‘n Pd(II) sout en ‘n ditioeter-gederivatiseerde resorsinareen het ‘n koordinasie verbinding met twee metaalkerne gelewer. Hierdie kompleks is deur middel van ‘n Heck-koppelingsreaksie vir katalitiese aktiwiteit getoets, maar het lae opbrengste gelewer in die koppeling van stireen en bromobenseen.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In this thesis we describe the synthesis of several new N-(n-propyl)-1-(2-pyridyl and quinolyl)-imine ligands (ML1-ML4) as well as peripheral functionalised iminopyridyl and iminoquinolyl poly(propylene-imine) dendrimeric ligands (DL1-DL8) with a 1,4- diaminobutane core. The dendrimeric ligands were obtained by modification of the peripheral groups of Generation 1 and Generation 2 poly(propylene-imine) dendrimers, (DAB-(NH2)n which are commercially available, with a series of aldehydes. All the ligands were fully characterised by ESI-mass spectrometry, elemental analysis, 1H&13C{1H}-NMR, FT-IR and UV/Vis spectroscopies. These ligands were utilised to synthesise Pd(II) and Cu(I) complexes using appropriate metal precursors. Some of mononuclear complexes, [N-(n-propyl)-(2-pyridyl and quinolyl) methanimine] dichloro Pd(II) complexes (C1-C4) and bis[N-(n-propyl)-(2-pyridyl and quinolyl) methanimine] copper(I) tetrafluoroborate complexes (C14) were structurally characterised. Pd(II) complexes adopted a distorted square-planar geometry around the metal centre while Cu(I) complex exhibit a distorted tetrahedral arrangement around the metal centre. Both Pd(II) and Cu(I) multinuclear complexes (metallodendrimers) were characterised using a range of analytical techniques. / AFRIKAANSE OPSOMMING: In hierdie tesis word die sintese van verskeie nuwe N-(n-propiel)-1-(2-piridiel) en kinolielimien ligande (ML1-ML4) sowel as gefunksioneerde imienopiridiel en imienokinoliel poli(propilien-imien) dendrimeriese ligande (DL1-DL8) beskryf. Die dendrimeriese ligande was behaal deur die modifikasie van perifere groepe van Generasie 1 en Generasie 2 poli(propilien-imien) dendrimere met ‘n reeks aldehiede. Alle ligande was volledig deur ESI-massaspektrometrie, elementele analiese, 1H en 13C{1H} – KMR, FT-IR en UV/Sigbare spektroskopie gekarakteriseerd. Hierdie ligande was gebruik om Pd(II) en Cu(I) komplekse te berei om van die gepaste metaal voorlopers te gebruik te maak. Sommige van die mono-kern komplekse, [N-(npropiel)-( 2-piridiel) en kinoliel metanimien] dikloor Pd(II), komplekse (C1-C4) en bis[N-(npropiel)-( 2-piridiel) metanimien] koper(I) tetrafloorboraat, kompleks (C14) was struktureël gekarakteriseerd. Pd(II) komplekse neem ‘n versteurde vierkant valk geometrie om die metaal senter aan, terwyl die Cu(I) kompleks, ‘n versteurde tetrahedriese opset rondom die metaal toon. Beide Pd(II) en Cu(I) multikern komplekse (metaaldendrimere) was deur ‘n verskeidenheid van analitiese tegnieke gekarakteriseerd.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The work presented in this dissertation describes the use of coaxial electrospinning of two miscible polymer solutions in the preparation of core-shell fibres with a semicrystalline core of poly(L-lactic acid) and an amorphous shell of poly(D,L-lactic acid). Additionally it describes using these fibres in the production of single polymer composite yarns and films. These materials can potentially be used in applications that require biodegradable and fibre-reinforced composite materials e.g. suture yarns. Traditional methods, such as TEM, when used to analyse the core-shell fibre structure were not successful with the polymer system used. A method was developed to validate core-shell fibre structure by selective dissolution of the shell material and correlating analyses of the separated components using differential scanning calorimetry (DSC) and optical rotation. The effects of solution concentration and flow rate on resultant core-shell fibre diameters were investigated. Core-solution flow rate was shown to be the most significant variable affecting the core and core-shell fibre diameters. A thermal processing window exists between the glass transition temperature of the amorphous PDLLA shell material and the crystalline melting temperature of the semicrystalline PLLA core material. Heating these core-shell fibres within this processing window resulted in flow and fusion of overlapping shells of these core-shell fibres at their surfaces while the fibrous core components remained intact and reinforced the resulting composite material. This approach was used to produce single polymer composite yarns and films. Thermal treatments on yarns were shown to increase crystallinity of the cores and therefore the modulus and yield strength of the fibres when compared to untreated yarns. / AFRIKAANSE OPSOMMING: Die werk wat in hierdie tesis voorgelê word, beskryf die gebruik van koaksiale elektro-spinnery van twee wedersydsoplosbare polimeeroplossings in die vervaardiging van kern-skilvesels met ‘n gedeeltelik-kristallyne kern van poli-Lmelksuur (PLLA) en ‘n amorfe skil van poli-D,L-melksuur (PDLLA). Verder beskryf dit die gebruik van hierdie vesels in die vervaardiging van enkel-polimeer saamgestelde-materiaalgarings en -films. Hierdie materiale kan moontlik gebruik word in toepassings wat bio-afbreekbare en veselversterkte saamgestelde materiale vereis, soos byvoorbeeld chirurgiese steke. Die polimeervesels wat in hierdie studie gebruik is, kon nie gekaraktiseer word met behulp van transmissie-elektronmikroskopie (TEM), wat gewoonklik gebruik word in die bestudering van kern-skilvesels, nie. ‘n Alternatiewe karakteriseringsmetode is ontwikkel om te bevestig dat die gevormde vesels wel ‘n kern-skilstruktuur het. Hierdie metode het behels dat die skil van die kern-skilvesel selektief opgelos is, waarna beide komponente (d.i. kern en skilmateriale) bestudeer is met behulp van differensiële skanderingskalorimetrie en optiese rotasie. Die invloed van polimeeroplossingskonsentrasie en –vloeitempo op die gevormde kern-skilvesels is daarna ondersoek en die vloeitempo van die kernoplossing is geïdentifiseer as die prosesinsetwaarde wat die mees beduidende invloed het op die deursnee van die vesels. Daar bestaan ‘n temperatuurinterval tussen die glasoorgangstemperatuur van die amorfe PDLLA skilmateriaal en die kristallyne smeltpunt van die gedeeltelikkristallyne PLLA kernmateriaal. Verwerking van die kern-skilvesels by ‘n temperatuur binne hierdie interval het gelei tot vervloeiing en samesmelting van die oorvleuelende skille van die kern-skilvesels, terwyl die veselagtige kernkomponente van die vesels heel gebly het en opgetree het as versterking binne-in die saamgestelde materiaal wat gevorm het. Hierdie benadering is gebruik om enkelpolimeersaamgestelde- materiaalgarings en –films te vervaardig. ‘n Vergelykende studie tussen onbehandelde en hitte-behandelde enkel-polimeer-saamgesteldemateriaalgarings het aangetoon dat die hittebehandeling gelei het tot ‘n verhoging in die kristalliniteit van die veselkerne en daarom ook ‘n verhoging in die modulus en breeksterkte van die garings tot gevolg gehad het.