Thesis (MSc)--Stellenbosch University, 1966. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (PhD (Chemistry and Polymer Science)--University of Stellenbosch, 2006. / Synthetic peptides derived from the active core of a natural antimicrobial peptide were used as a template for the design of novel bolaamphiphilic peptides and hybrid molecules. The amphiphilic character of the original compounds was modified by using non-natural amino acids (AAs) – such as ω-AA – and varying the hydrophobic content. The outcomes of these modifications were studied focusing on structural and biological properties. Because of the bolaamphiphilic character, the alternation of polar and non-polar AAs and the use of hydrophobic AAs such as tyrosine and leucine, these novel molecules were designed to undergo self-assembly in response to certain stimuli (e.g. a pH increase). This significant property was investigated by means of different tools, such as fluorescence measurements, electron microscopy (EM), Fourier transform infrared spectroscopy (FT-IR) and circular dichroism (CD). By using fluorescence it was possible to determine the critical aggregation concentration (CAC) of the new compounds. Differences in amino acid composition, which were reflected into diverse secondary structures and hydrophobicity (H), resulted in different CAC values and aggregation profiles. The data were consistent with the literature and showed that (i) the aggregation of these basic compounds was triggered by a pH increase, (ii) the use of hydrophobic AA highly augmented the self-assembly tendency while (iii) the presence of proline strongly reduced it. EM revealed the morphology of the peptide assemblies: microtubes and microvesicles were identified and characterised by dimensions of 500 nm to 2 μm. The presence of 3-way junctions and vesicles budding out of the microtubes demonstrated that the self-assembly is a dynamic process. The aggregation was confirmed by FT-IR spectroscopy, by studying the dried peptide assemblies and the significant spectral signs the process left, especially in the amide II envelope. The relationship between hydrophobicity and self-assembly was expanded by experimentally and theoretically determining the hydrophobic content of the novel bolaamphiphiles. Data from liquid chromatography and computational calculations (two common ways used to determine the hydrophobicity of a given molecule) correlated well with the tendency to self-assemble, as expressed by CAC values. Importantly, some structural parameters (such as the presence of β-turn induced by proline) also showed significant influence on the aggregation, highly limiting the role of the peptides’ hydrophobicity. These novel peptide bolaamphiphiles displayed a very low haemolytic action and retained some antimicrobial activity at high concentrations against both Gram-positive and -negative bacteria. Unfortunately, the activity was greatly reduced at low concentrations, as clearly demonstrated by the use of two antimicrobial tests. The inability to provoke cell lysis was also evident when using liposomes mimicking a negative bacterial membrane. The loss of activity is possibly related to the modifications of the three-dimensional structure caused by the use of ω-AA and proline, which strongly alter the secondary structure. The results of this study were valuable in terms of understanding the relationships between self-assembly and structural parameters, such as AA compositions, hydrophobicity and secondary structure. Possible applications of the synthesised compounds were however limited as a result of the loss of the biological activity at low concentrations.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2008. / This dissertation can be broken into two parts comprising different strategies to synthesise novel poly-amino acid based polymers. The use of recently developed nickel(0) and cobalt(0) metal catalysts for the living polymerization of α-amino acid-N-carboxyanhydrides (NCAs) to synthesise novel poly-amino acid polymers, comprising a polar, hydrophilic block and a neutral hydrophobic block, were investigated in the first part of this study. The hydrophilic block was made up of a random sequence of arginine (Arg, R), glycine (Gly, G) and aspartic acid (Asp, D) - poly-RGD. This was followed by a polyleucine (Leu, L) hydrophobic block. Success was limited with this system due to polymer precipitation during the polymerization reaction. Because of this precipitation, the amino acid composition of the hydrophilic block was changed to a random sequence of glutamic acid (Glu, E), cystein (Cys, C) and aspartic acid – poly-ECD. Here also, the success was limited because of polymer precipitation. A novel approach to the synthesis of hybrid poly-amino acid – synthetic polymer materials constitutes the second part of this study. The final polymeric structure can be described as a carboxylic acid functionalized polyethylene glycol (PEG) sheathed polylysine polymer. The technology involves the synthesis of a lysine NCA functionalized at the ε-amino group with an α,ω-bis(carboxymethyl) ether PEG. The distal carboxylic acid group was protected as a benzyl ester during synthesis and subsequent polymerization of the PEG-lysine-NCA macro-monomer. The polymerization was successfully initiated using n-butyl amine to form short homopolymer strands. Copolymerization with lysine-NCA was also achieved as well as the successful initiation using a generation 1.0 dendritic amine initiator, N,N,N’,N’-tetrakis(3-aminopropyl)-1,4-butanediamine (DAB-Am-4). These polymers were characterized by 1H NMR.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Synthesis and structural characterization of two novel cationic and three new neutral reversible addition–fragmentation chain transfer (RAFT) agents is described. The cationic RAFT agents bear a quaternary ammonium group: N,N-dimethyl-N-(4- (((phenylcarbonothionyl)thio)methyl)benzyl)ethanammonium bromide (PCDBAB) and N-(4-((((dodecylthio)carbonothioyl)thio)methyl)benzyl)-N,N-dimethylethanammonium bromide (DCTBAB). The three neutral RAFT agents synthesized are 1,4- phenylenebis(methylene)dibenzene carbodithioate (PCDBDCP), didodecyl-1,4- phenylenebis(methyllene)bistrithiocarbonate (DCTBTCD) and 11-(((benzylthio)carbonothioyl) thio)undecanoic acid (BCTUA). The self-assembly behaviour in diluted aqueous solutions of the cationic RAFT agents, PCDBAB and DCTBAB, is described. The self-assembly behaviour was promoted by the presence of the thiocarbonyl- thio group on the RAFT agents, in addition to the overall chemical structure of the surfactant that also influence self-assembly. The RAFT agents were used for the bulk or miniemulsion RAFT-mediated controlled free-radical polymerization in the presence of clay to yield polymer–clay nanocomposites (PCNs). Bulk polymerization resulted in PCNs with better control of molar mass and polydispersity index (PDI) values when compared to PCNs prepared by miniemulsion polymerization. In both bulk and miniemulsion polymerizations the molar masses and PDI values were dependent on the amount of clay and RAFT agent present in the system. Free-radical bulk neutral RAFT agent-mediated polymerization resulted in PCNs with predominantly intercalated morphology. This was attributed to radical–radical coupling of the initiator anchored onto the clay galleries on which polymerization took place. On the other hand, when the cationic RAFT agent anchored onto clay, i.e. RAFT-modified clay was used, bulk polymerization resulted in predominantly exfoliated PCNs. However, miniemulsion polymerization carried out in the presence of the RAFT-modified clays resulted in PCNs with a morphology that ranged from partially exfoliated to intercalated morphology, as the clay loading was increased. The changing morphology for miniemulsion-based PCNs was attributed to the decreasing molar mass as the clay loading was increased. The PCNs obtained had enhanced thermo-mechanical properties as a result of the presence of clay. The thermo-mechanical properties depended on the molar mass, PDI, clay loading, and the morphology of the PCNs.

Thesis (PhD (Chemistry and Polymer Science))—University of Stellenbosch, 2006. / This study describes the exploitation of numerous donor ligand possibilities presented by selected nitrogen-rich heterocyclic ligands towards gold(I). The preparation and structural characterisation of novel gold(I) complexes, apart from conventional gold(I) bonding possibilities, also encompassed a study of bi- and polytopic bonding modes within a range of multifunctional ligands.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / In this thesis the main capillary electrodriven chromatographic techniques (i.e. Capillary Electrochromatography CEC, Micellar Electrokinetic Chromatography MEKC and Microemulsion Electrokinetic Chromatography MEEKC) were compared in terms of column manufacturing, fundamental chromatographic performance, and some applications were developed. The first stage of this thesis aimed at developing improved packed and open tubular CEC columns. For the manufacturing of packed CEC columns, the frit-burning step proved of critical importance, together with the slow build-up of the packed bed. The making of open tubular columns is a relatively simple, "one pot" sol-gel reaction taking place in mild conditions. The nature of the gel and the resulting selectivity of the column could easily be changed by changing the precursors. In a second stage of this thesis the packed and open tubular CEC columns were evaluated chromatographically and compared with the results obtained by MEKC and MEEKC. All electrodriven separation techniques showed high efficiencies. The selectivity proved easier to tune with sol-gel chemistry for the making of open tubular columns. Resolution is acceptable for packed CEC, MEKC and MEEKC. For peak capacity, CEC has the advantage of a practically non-limited elution time, while MEKC and MEEKC suffer of the drawback of the existence of an elution window which is limited in time by the elution of the micelles. Some applications were developed in this study on open tubular CEC columns and for the packed CEC columns. Various sugars derivatized with 9- aminopyrene-1,4,6-trisulfonic acid (APTS) could be separated with open tubular CEC, using an octyl, amino or cyano stationary phase. Open tubular columns containing α, β and γ cyclodextrins attached to the stationary phase were developed. This approach proved promising for the separation of positional isomers. A method was developed for the analyses of a mixture of carbamates and for several steroids with packed column CEC directly coupled with MS.

Dissertation (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This study comprises the preparation and characterisation of various novel organometallic species of gold(I) by employing a range of anionic group 6 metal Fischer-type carbene complexes and group 6 metal-acyl complexes as synthons of the organic moieties introduced to the gold(I) electrophiles. The main objectives of this work are to develop the use of Fischer-type carbene complexes as synthons in the preparation of novel organometallic species along unusual reaction pathways and, in doing so, to expand the organometallic chemistry of gold(I), especially Au-C bond formation reactions. By reacting various β-CH acidic Fischer-type alkoxy/dialkylamino/ alkthio(methyl)carbene complexes, first with a base, and then with a gold(I) electrophile (Ph3PAu+), easy access to vinyl ether/dialkylamine/thioether complexes of gold(I) coordinated to M(CO)5 (M = Cr, Mo, W) fragments, is obtained. When methyl alkoxy- or dialkylaminocarbene complexes are employed, coordination of the novel alkoxyvinyl-gold(I)PPh3 and dialkylaminovinyl-gold(I)PPh3 species to the M(CO)5 fragments occurs in an asymmetrical fashion through the vinyl functionalities of the novel gold(I) species. This usually unstable coordination mode for vinyl ethers is stabilised by delocalisation of partial positive charges from the α-gold vinyl carbon atoms to either the gold(I)PPh3 fragment [for η2-{alkoxyvinyl-gold(I)PPh3}M(CO)5 complexes] or the nitogen atoms of the vinyl amine group [for η2-{dialkylaminovinylgold( I)PPh3}M(CO)5 complexes]. In the latter complexes this delocalisation occurs to such an extent that these complexes are best described as zwitterions. The corresponding negative charges in the bimetallic complexes reside on the M(CO)5 fragments. As a representative example, uncoordinated ethoxyvinyl-gold(I)PPh3 was isolated in high yield via a ligand replacement reaction with PPh3. When Fischer-type alkthio(methyl)carbene complexes are employed in this conversion, novel sulphur coordinated {alkthiovinyl-gold(I)PPh3}Cr(CO)5 complexes are formed.The reaction mechanism involved in these conversions is believed to be the gold(I) analogue of the hydrolysis of Fischer-type carbene complexes. In this mechanism the bimetallic η2-vinyl ether coordinated {alkoxyvinyl-gold(I)PPh3}M(CO)5 complexes represent stabilised gold(I) analogues of postulated transition states in the hydrolytic decomposition of Fischer-type alkoxycarbene complexes. The term aurolysis is conceived to describe the conversion when Ph3PAu+ is employed as electrophile instead of H+. The formation of the bimetallic η2-vinyl ether coordinated complexes in the current conversion, furthermore, strongly supports the existence of similar transition states in the hydrolytic decomposition of Fischer-type alkoxycarbene complexes. This mechanism is also accepted for the formation of analogous η2-{dialkylaminovinyl-gold(I)PPh3}M(CO)5 and {alkthiovinyl-gold(I)PPh3}-S Cr(CO)5 complexes when β-CH deprotonated Fischer-type dialkylamino- and alkthiocarbene complexes are employed in this reaction. The reaction of anionic group 6 metal-acyl complexes and their nitrogen analogues, N-deprotonated Fischer-type aminocarbene complexes, leads to the formation of acylgold(I) and novel imidoylgold(I) complexes coordinated to M(CO)5 (M = Cr, W) fragments. In the previous complexes poor stabilisation of the M(CO)5 fragments allows halide anions to readily form ionic adducts with these groups. This characteristic of these products provides a useful reaction pathway to the first example of a free acylgold(I) complex, benzoyl-AuPPh3. Coordination of the imine nitrogen atom to the M(CO)5 fragments in the analogous bimetallic imidoylgold(I)-M(CO)5 complexes is much stronger. These complexes are remarkably stable and could even be effectively isolated by means of low temperature silica gel chromatography. As a preliminary reaction mechanism for this conversion we propose a mechanism that is closely related to the aurolysis mechanism described above. The only difference is that, instead of formal reductive elimination of vinyl ethers/amine/thioether complexes of gold(I) from the M(CO)5 fragments, acyl and imidoyl complexes of gold(I) are produced in this step. Furthermore, the (Z)- stereoisomers of the bimetallic imidoylgold(I)-M(CO)5 complexes generated in this conversion are exclusively obtained.A second N-deprotonation-auration reaction sequence performed on suitable examples of the bimetallic imidoylgold(I)-M(CO)5 complexes yields, as the only isolable product, a novel triangular Au2Cr cluster complex, cis-{η2-(Ph3PAu)2} PPh3Cr(CO)4. This complex is the isolobal equivalent for the unstable molecular hydrogen complex, (η2-H2)PPh3Cr(CO)4, and exhibits the shortest known Au-Au separation between two gold atoms in cluster complexes of the type Au2M. Finally, two novel and vastly different molecular structures of closely related anionic benzoylpentacarbonyl tungstates, one with Li+ as counterion and another in which exactly half the Li+-cations have been replaced by protons, highlight the importance of hydrogen bonding and ion-dipole interactions in determining the solid state structure of such complexes. / AFRIKAANSE OPSOMMING: Hierdie studie behels die bereiding en karakterisering van verskeie nuwe organometaalkomplekse van goud(I). Hierdie komplekse is berei deur gebruik te maak van n wye reeks anioniese groep 6 metaal Fischer-tipe karbeenkomplekse asook anioniese groep 6 metaal asielkomplekse as sintetiese ekwivalente vir die organiese fragmente wat gedurende die sintese aan die goud atoom gebind word. Die hoofdoel van hierdie studie is om die gebruik van Fischer-tipe karbeenkomplekse as sintetiese voorgangers in die bereiding van nuwe organometaalverbindings te ontwikkel en om sodoende ook die organometaalchemie van goud verder uit te bou. Veral die ontwikkeling van nuwe sintetiese metodologieë vir die bereiding van Au-C bindings is hier van belang. Verskeie Fischer-tipe alkoksie-/dialkielamino-/alktio-(metiel)karbeenkomplekse met suuragtige waterstofatome geleë op die β-metallo-koolstofatoom is eers onomkeerbaar gedeprotoneer. Byvoeging van die goud(I) elektrofiel, Ph3PAu+, lei - volgens n ongewone reaksiemeganisme - tot die vorming van onderskeie vinieleter-, dialkielvinielamien- en vinieltioeterkomplekse van goud(I). Hierdie komplekse is verder ook op verskillende wyses aan M(CO)5 fragmente (M = Cr, Mo, W) gekoördineer. Die vinieleter- en vinielamienkomplekse van goud(I), wat vorm wanneer alkoksie- en dialkielaminokarbeenkomplekse onderskeidelik in hierdie sintese aangewend word, koördineer onsimmetries deur hulle viniel dubbelbindings aan die vrygestelde M(CO)5-groepe. Hierdie normaalweg onstabiele vorm van vinieleterkoördinasie, word gestabiliseer deur delokalisering van positiewe lading vanaf die α-goud viniel koolstofatoom na die AuPPh3-fragment [vir die η2-{alkoksievinielgoud( I)PPh3}M(CO)5 komplekse] óf na die stikstofatoom van die dialkielvinielamien groep [vir die η2-{dialkielaminoviniel-goud(I)PPh3}M(CO)5 komplekse]. Laasgenoemde komplekse kan as zwitterione beskryf word. Die onderskeie negatiewe ladings in hierdie komplekse bevind hulle hoofsaaklik op die M(CO)5 groepe. Sterk koördinerende ligande (bv. PPh3) verplaas die onsimmetriese viniel eter vanaf die M(CO)5-fragment. Só kon, as n voorbeeld, die vrye etoksievinielgoud( I)PPh3-kompleks met n hoë opbrengs berei word. Wanneer β-gedeprotoneerdeFischer-tipe tiokarbeenkomplekse met Ph3PAu+ reageer, vorm swawel gekoördineerde {tioviniel-goud(I)PPh3}Cr(CO)5 bimetalliese komplekse in stede van die π-komplekse. Dit word voorgestel dat in die bogenoemde reaksies die goud(I)elektrofiel dieselfde rol vervul as die proton gedurende die hidrolise van Fischer-tipe alkoksiekarbeenkomplekse. Die bimetalliese, η2-vinieleter-gekoördineerde {alkoksieviniel-goud(I)PPh3}M(CO)5-komplekse hier berei verteenwoordig dus stabiele goud(I) analoë van voorgestelde tusseprodukte in so ’n meganisme. Die term aurolise word voorgestel om die geval waar Ph3PAu+ in stede van H+ as elektrofiel aangewend word te beskryf. Die vorming van bimetalliese, η2-vinieletergeko ördineerde komplekse in die huidige reaksie ondersteun die moontlike vorming van die voorgestelde tussenprodukte tydens die hidrolise van Fischer-tipe alkoksie(metiel)karbeenkomplekse. ’n Soortgelyke meganisme kan ook gebruik word om die vorming van die η2-{dialkiellamienviniel-goud(I)PPh3}M(CO)5- en {alktioviniel-goud(I)PPh3}-S Cr(CO)5-komplekse vanuit β-CH gedeprotoneerde Fischer-tipe dialkielamino- en tiokarbeenkomplekse en Ph3PAuCl te interpreteer. Die reaksie van anioniese groep 6 oorgangsmetaal metaal-asielkomplekse en hulle stikstofanaloë, N-gedeprotoneerde Fischer-tipe aminokarbeenkomplekse, lewer onderskeidelik asiel- en imidoielkomplekse van goud(I) wat aan M(CO)5 fragmente (M = Cr, W) koördineer. Die goud(I)asiel-M(CO)5 koördinasie deur die asielsuurstofatoom is baie swak en die M(CO)5-eenheid in hierdie komplekse word maklik deur haliedanione en sekere oplosmiddel molekules verplaas. Die haliedanione vorm anioniese addukte met the M(CO)5 fragmente. Hierdie eienskap van die bimetalliese komplekse verskaf sodoende n gerieflike sintetiese roete na die eerste voorbeeld van n vrye asielgoud(I)-kompleks, bensoiel-AuPPh3. Koördinasie van die imienstikstofatoom aan M(CO)5-groepe in die bg. imidoielkomplekse is egter veel sterker. Die bimetalliese {imidoielgoud(I)}M(CO)5-komplekse is verbasend stabiel en kan selfs effektief deur middel van lae temperatuur SiO2-kolomkromatografie geïsoleer word. n Soortgelyke reaksie meganisme as wat voorgestel word vir die aurolise van Fischer-tipe karbeenkomplekse word voorgestel vir hierdie reaksie. Die enigste verskil is dat die formele reduktiewe eliminasie van n viniel-eter, -amien of -tioeter vervang word met die vorming van asiel- of imidoielkomplekse van goud(I). Verder word die (Z)-isomere van die bimetalliese {imidoielgoud(I)}M(CO)5-komplekse uitsluitlik in hierdie reaksie verkry. Wanneer geskikte voorbeelde van bimetalliese {imidoielgoud(I)}M(CO)5-komplekse n tweede keer gedeprotoneer word en gereageer word met Ph3PAuCl, is die enigste isoleerbare produk van die reaksie n driehoekige Au2Cr troskompleks, nl. cis-{η2- (Ph3PAu)2}PPh3Cr(CO)4. Hierdie verbinding dien as n isolobale model vir die onstabiele molekulêre waterstof kompleks , (η2-H2)PPh3Cr(CO)4, en besit verder die kortste Au-Au afstand tussen twee goud atome in driehoekige troskomplekse wat nog tot dusvêr gerapporteer is. Laastens is die kristalstrukture van twee nou verwante anioniese {bensoiel}W(CO)5- komplekse bepaal. Die enigste verskil tussen die hierdie twee verbindings is dat die een slegs Li+ as teenioon bevat terwyl presies die helfte van die Li+-teenione in die tweede struktuur deur protone verplaas is. Hierdie klein verskil in samestelling veroorsaak egter drastiese verskille in die kristalstrukture van hierdie verbindings. Die belangrikheid van waterstof bindings en ioon-dipool interaksies in die bepaling van die vastetoestandstrukture van sulke verbindings word hierdeur beklemtoon.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The use of chiral oxazoline directed lithiation provides a highly diastereoselective (up to >99% de) route to meta functionalised inherently chiral calixarenes. This methodology can be used on both the butylated and debutylated calixarene systems and is tolerant of a wide range of different electrophillic quenches allowing access to a structurally diverse range of inherently chiral metafunctionalised calixarenes. The oxazoline directing group can be removed via hydrolysis, generating a range of functionalised calixarene carboxylic acids in high ee. We also demonstrate that the use of derivative alkyllithiums such as cyclopentyl lithium can provide significantly enhanced diastereoselectivity over the conventional organolithiums such as sec-butyl lithium, when employed in ortholithiation reactions of this nature. The differences in diastereoselectivity associated with the different alkyllithiums can be tied, in certain cases, to the steric bulkiness associated with the individual reagents. In this regard we have found that the use of the so called Tolman angle or cone angle approach allows quantification of the relative steric bulk of the alkyllithium. We also detail that the oxazoline directing group provides a hitherto unknown ability to be diastereoselectively tuned through the choice of the ligand system in the ortholithiation reaction. In this regard the development of a series of diglyme based ligands have proved to provide a highly diastereoselective means of inverting the chirality from that which the use of the conventional TMEDA ligand is able to generate (up to –92% de). The use of diglyme ligands to invert the sense of chirality is also shown to occur on the ferrocenyloxazoline system and presents an apparently general and hitherto unknown facet of asymmetric oxazoline directed ortholithiation. This diglyme induced inversion has been shown to be controlled through a secondary nitrogen coordinated mechanism that is able to operate with chiral oxazolines. / AFRIKAANSE OPSOMMING: Die gebruik van chirale oksasoliengerigte litiëring verskaf ’n hoogs diastereoselektiewe (tot en met >99% do) roete om metagefunksionaliseerde, inherente chirale calixareen produkte te sintetiseer. Deur gebruik te maak van verskillende elektrofiele kan die metodologie toegepas word op beide gebutileerde en de-gebutileerde calixareen sisteme om ’n reeks uiteenlopende inherente chirale, meta-gefunksionaliseerde calixareen produkte te vorm. Die oksasolien groep kan daarna verwyder word deur hidroliese om ’n reeks gefunksionaliseerde calixareenkarboksielsure te vorm in baie hoë eo. Ons het ook gedemonstreer dat die gebruik van afgeleide alkiel-litiums, soos siklopentiel-litium, kan bydrae tot aansienlik verhoogde diastereoselektiwiteit as dit vergelyk word met meer algemene organolitiums soos sekbutiellitium, tydens ortolitiëring reaksies van hierdie natuur. Die verskille in diastereoselektiwiteit kan verbind word, in sekere gevalle, tot die steriese bonkigheid van die individuele reagense. Deur gebruik te maak van die sogenaamde Tolmanhoeke of die koniesehoek benadering is dit moontlik om die relatiewe steriese bonkighied van alkiellitiums te kwantifiseer. Daar was ook bepaal dat die oksasoliengroep die ongekende vermoë besit om die diastereoselektiwiteit van die produk te stem deur die keuse van verskillende ligand sisteme tydens die ortolitiëring reaksie. Daar was bepaal dat die chiralitiet van die produkte omgekeer kan word op ’n hoogs diastereoselektiewe manier, deur gebruik te maak van ’n reeks ontwikkelde diglymegebaseerde ligande, indien dit vergelyk word met die produkte wat deur die konvensionele TMEDA gegenereer was (tot en met –92% do). Die gebruik van diglyme ligande was ook getoets op ferroseenoksasolien sisteme en dit was bevind dat dieselfde omkering in chiraliteit ook plaasvind wat aanleiding kan gee tot 'n oënskynlik algemene en tot nou toe onbekende faset van asimmetriese oksasoliengerigte orto-litiëring. Dit is bepaal dat hierdie diglyme geïnduseerde omkering in chiraliteit beheer word deur middel van 'n sekondêre stikstofgekoördineerde meganisme, wat in staat is om saam te werk met chirale oksasoliene.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Multiphase copolymers generally consist of copolymers where the disparate natures of each of the segments results in complex phase-segregated morphologies in the solid state. The outstanding properties and wide range of applications of multiphase copolymers has led to the need for more sophisticated synthesis methods to produce copolymers with controlled structures. Associated with developments in synthetic methods is the need to develop suitable techniques to characterize these materials in order to obtain a better understanding of their structure–property relationships. The synthesis of multiphase copolymers presents many challenges. These are related to the nature of the molecular requirements, were the monomers of each of the different components may not be polymerized by all available polymerization techniques. This has led to the need to combine different polymerization techniques to overcome such limitations. The focus of this study is the combination of living controlled polymerization techniques, namely anionic polymerization and RAFT polymerization, with hydroboration/autoxidation, to produce non-polyolefin block and graft copolymers. Block copolymers were synthesized by coupling anionic polymerization and hydroboration/autoxidation reactions. The first block segment was prepared via anionic polymerization, and then end-functionalized with a suitable functional group (e.g. an allyl group). A hydroboration/autoxidation reaction was then used to initiate the polymerization of the second block by the slow addition of oxygen at room temperature. Graft copolymers were synthesized using the 'grafting from' technique, by coupling RAFT copolymerization with hydroboration/autoxidation reactions. The backbone polymer was synthesized via RAFT copolymerization of symmetric and asymmetric monomer, after which a hydroboration/autoxidation reaction was carried out to produce graft copolymers. The hydroboration/hydroxylation reaction could also be used to modify an unsaturated polymer chain. The EPDM rubber chain was modified by transforming the double bond into an hydroxyl group, which could undergo an esterification reaction with an acid chloride RAFT agent to produce the multifunctional RAFT polymer. This was used for the controlled living free radical polymerization of the graft chains. Significant amounts of homopolymerization in addition to graft formation were obtained. Solid state NMR (SS NMR) and positron annihilation lifetime spectroscopy were used to determine the compositional phase segregation point in the graft copolymers. The spin diffusion data from the SS NMR provided insight into the seemingly anomalous positron data at the phase segregation point. It is demonstrated how these two techniques can provide complimentary data on the solid state morphology of these multiphase materials. / AFRIKAANSE OPSOMMING: In die algemeen bestaan multifase kopolimere uit segmente van verskillende aard wat komplekse fase-geskeide-morfologie in die vastetoestand tot gevolg het. Die uitstekende eienskappe en wye reeks toepassings van multifase kopolimere het daartoe gelei dat meer gesofistikeerde sintesemetodes vir die bereiding van kopolimere met gekontrolleerde strukture nodig was. Gepaardgaande met verwante ontwikkelings op die gebied van sintesemetodes was dit nodig om gepaste analitiese tegnieke te ontwikkel vir die karakterisering van hierdie verbindings, ten einde die struktuur–eienskap verwantskap van hierdie materiale beter te verstaan. Daar is egter baie uitdagings m.b.t. die sintese van hierdie multifase kopolimere. Dit is afhanklik van die aard van die molekulêre vereistes waar die monomere van elk van die verskillende komponente nie deur alle beskikbare polimerisasietegnieke gepolimeriseer kan word nie. Dit het daartoe gelei dat verskillende polimerasietegnieke gekombineer is ten einde hierdie beperkinge te oorbrug. Die fokus van hierdie studie is die kombinering van lewende vry-radikaal gekontrolleerde polimerisasietegnieke, naamlik anioniese polimerisasie en RAFTpolimerisasie, met hidroborering/outoksidasie, om nie-olefiniese blok- en entkopolimere te berei. Blok-kopolimere is berei deur die koppeling van anioniese polimerisasie en hidroborering/outoksidasie reaksies. Die eerste bloksegment is berei via anioniese polimerisasie en daarna is endfunksionering met 'n geskikte funksionele groep (bv. 'n allielgroep) bewerkstellig. Daarna is 'n hidroborering/outoksidasie reaksie gebruik om die polimerisasie van die tweede blok te inisieer d.m.v. die stadige toevoeging van suurstof by kamertemperatuur. Entkopolimere is berei deur gebruik te maak van die 'ent-vanaf' tegniek, d.m.v. die koppeling van RAFT-kopolimerisasie met hidroborering/outoksidasie reaksies. Die rugraatpolimeer is berei d.m.v. kopolimerisasie van simmetriese en nie-simmetriese monomere waarna die hidroborering/outoksidasie reaksie uitgevoer is om sodoende entkopolimere te vorm. Die hidroborering/hidroksilasie reaksie kon ook gebruik word om 'n onversadigde polimeerketting te wysig. Die EPDM rubberketting is gewysig deur die omskakeling van die dubbelbinding in 'n hidroksielgroep, wat dan 'n esterifikasie reaskie kon ondergaan met 'n suurchloried-RAFT verbinding, om sodoende die multifunksionele RAFT-polimeer te vorm. Dit is gebruik vir die gekontrolleerde lewende vry-radikaalpolimerisasie van die entkettings. Behalwe entvorming is 'n hoë mate van homopolimerisasie waargeneem. Vastetoestand KMR (VS KMR) en positronvernietigingsleeftydspektroskopie is gebruik om die saamgestelde faseskeidingspunt in die entkopolimere te bepaal. Die spindifffusie data van VS KMR het insig verleen aan die oënskynlik onreëlmatige positrondata by die faseskeidingspunt. In die studie is bewys hoe hierdie twee tegnieke komplimentêre data kan lewer m.b.t. die vastetoestandmorfologie van hierdie multifase materiale.

Thesis (PhD)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The analysis of Fischer–Tropsch–derived (FT–derived) synthetic crude and derived products is very challenging because of the highly complex nature of these products. In this study, the use of comprehensive multidimensional gas chromatography (GCxGC) with time-of-flight mass spectrometry (TOF-MS) and flame ionisation detection (FID) was investigated for the analysis of these products and the technique was found to be invaluable for the analysis of these complex mixtures. The compositions of FT synthetic crude, produced at low temperature (LT–FT) and high temperature (HT–FT) processes were compared and the effect that changes in FT reaction temperature has on product formation was investigated. Results for conventional onedimensional GC (1D-GC) and GCxGC were compared. It was found that conventional 1D–GC does not have sufficient peak capacity to separate the thousands of compounds in the HT FT products. GCxGC provides a huge peak capacity of tens-of-thousands to separate highly complex mixtures. Structured chromatograms, where groups of compounds with similar properties are grouped together, aid in peak identification. Moreover, sensitivity at low microgram per milliliter levels is obtained. These attributes enabled accurate analysis of various complex feed and product streams in the FT refinery, and also various final fuel products. The use of GCxGC alone was demonstrated, and also combined with high performance liquid chromatography (HPLC), supercritical fluid chromatography (SFC) and nuclear magnetic resonance (NMR) when even more separation power was needed. HPLC–GCxGC enabled the separation of alkene and cyclic alkane compound classes in oligomerisation products. These compound classes have similar mass spectra, elute in adjacent regions and co–elute even to some extent on the GCxGC contour plot, making differentiation difficult. SFC is a good replacement for HPLC for these applications because it does not use solvents as mobile phases. CO2 is easily evaporated after the separation and does not interfere with the GCxGC separation of the analytes. SFC is also a very good technique to separate the compound classes of alkanes, alkenes, aromatics and oxygenates, and is therefore highly complementary to GCxGC. The combination of GCxGC with NMR data was also found to be very valuable for the identification of branched alkane isomers in LT–FT diesels. GCxGC provides excellent separation of individual compounds but the identification of isomers (except for mono–methyl branching) is difficult because the mass spectra of most of these isomers are similar and not all compounds are in the mass spectral libraries. NMR, on the other hand, is able to distinguish between the individual types of branched isomers but has limited separation power for the complex mixtures. By combining the two techniques, the best of both was obtained. The study found GCxGC to be invaluable for the analysis of the highly complex FT–derived products, while its combination with other techniques such as HPLC, SFC and NMR provided even more separation power. / AFRIKAANSE OPSOMMING: Die hoogs komplekse samestelling van sintetiese ru–olie en afgeleide produkte, afkomstig van Fischer–Tropsch (FT) sintese, bied groot uitdagings aan die analis. Die studie het die gebruik van GCxGC met ’n TOF-MS en FID bestudeer vir die analise van FT produkte en het bevind dat die tegniek van onskatbare waarde is vir die analise van die hoogs komplekse mengsels. Die samestellings van produkte van lae- en hoë-temperatuur FT prossesse is vergelyk en die effek van ’n verhoging in die reaksie–temperatuur op die produk samestelling is ondersoek. Resultate vir 1D–GC and GCxGC is vergelyk en dit was duidelik dat 1D-GC nie naastenby voldoende piekkapasiteit het om al die komponente van die produkte wat tydens die hoëtemperatuur prosses gevorm word, te kan skei nie. Die GCxGC se piekkapasiteit daarteenoor is in die orde van tienduisende wat die skeiding van hoogs komplekse mensels moontlik maak terwyl die tegniek hoogs gestruktureerde kontoerplotte verskaf wat help met identfikasie van komponente. Die tegniek is verder ook baie sensitief en kan komponente op lae μg/mL vlakke waarneem. Hierdie eienskappe het akkurate analise van verskeie FT produkstrome moontlik gemaak. Die kombinasie van GCxGC met HPLC, SFC en KMR het selfs meer skeidingskrag verskaf waar nodig. HPLC–GCxGC het die skeiding van alkene en sikliese alkane moontlik gemaak. Hierdie komponent klasse se massaspektra is feitlik dieselfde en terselfdertyd elueer die twee groepe reg langs mekaar, en oorvleuel soms selfs tot ’n mate, op die GCxGC kontoerplot, sodat dit moeilik is om daartussen te onderskei. SFC is ’n goeie alternatief vir HPLC in meeste toepassings aangesien die tegniek net CO2 gebruik, wat maklik verdamp by kamertemperatuur en nie oplosmiddels gebruik wat se pieke steur met die van die laekookpunt komponente op die GCxGC kontoerplot nie. Skeidings van die komponentgroepe alkane, alkene, aromate en oksigenate is moontlik met SFC en daarom komplimenteer dit die GCxGC skeiding goed aan. Die kombinasie van GCxGC met kern–magnetiese resonansie (KMR) is van waarde gevind om die verskillende tipes vertakkings in ’n lae-temperatuur FT diesel te identifiseer. GCxGC verskaf uitstekende skeiding van individuele komponente maar die identifikasie van die verskilende isomere, behalwe vir die mono-metiel vertakkings, is moeilik aangesien die massaspektra van baie van die komponente soortgelyk is en die komponente nie in die massa spektrum–biblioteke voorkom nie. KMR, aan die ander kant, kan tussen die individuele vertakkings onderskei maar het beperkte skeidingskrag vir komplekse mensels. Deur die twee tegnieke te kombineer is die beste van albei tegnieke bekom. Die studie het bevind dat GCxGC van onskatbare waarde is vir die analise van die komplekse sintetiese FT produkte terwyl die kombinasie met ander tegnieke soos HPLC, SFC and KMR selfs meer skeidingskrag verskaf.