Thesis (MSc)-- Stellenbosch University, 2012. / ENGLISH ABSTRACT: Over the past two decades, field flow fractionation (FFF), as a polymer characterization technique, has become cutting edge technology. The demand for molar mass and size characterisation of complex polymer systems has increased, especially in cases where classical calibration techniques such as size exclusion chromatography (SEC) has shown several shortcomings. FFF is a technique resembling chromatography. It has several significant advantages over SEC, especially for the characterisation of ultrahigh molar mass (UHMM), branched and gel-containing polymers. In this study, polybutadienes, which often contain the abovementioned species, were analysed by SEC and asymmetric flow field flow fractionation (AF4). Both separation techniques were coupled to refractive index and multi-angle laser light scattering detection. Similarly, polyrotaxanes, which are polymers with complex and unique molecular architectures, were also investigated. Results showed that AF4 can explicitly be used as a superior tool over SEC. In the case of UHMM polybutadienes, much higher molar masses could be detected by AF4, due to the absence of shear degradation which is often encountered in SEC. Gel-containing species could be detected by AF4 as no filtering is required prior to injection. Abnormal retention behaviour, a phenomenon often encountered in UHMM branched polymers, was observed in SEC analysis of the polyrotaxanes materials. AF4 provided sufficient separation from low to high molar masses, without out any irregularities. / AFRIKAANSE OPSOMMING: Gedurende die afgelope twee dekades het veldvloeifraksionering (FFF) as ‘n polimeerkarakteriseringstegniek groot veld gewen. Die aanvraag na molekulêre massa en groottekarakterisering van komplekse polimeersisteme het toegeneem, veral in die gevalle waar klassieke kalibrasietegnieke soos grootte-uitsluitingschromatografie (SEC) etlike tekortkominge getoon het. FFF is ‘n tegniek soortgelyk aan chromatografie, en het voorheen bewys dat dit oor ‘n redelike aantal voordele bo SEC beskik, veral in die geval van ultrahoë molekulêre massa- (UHMM-), vertakte- en jelbevattende spesies. In die huidige studie is polibutadieenpolimere, wat dikwels bogenoemde spesies bevat, geanaliseer met behulp van SEC en onsimmetriese vloei-veldvloeifraksionering (AF4). Beide skeidingstegnieke is gekoppel aan ‘n brekingsindeks en multihoek-laserligverstrooiingsdetektors. Op dieselfde wyse is polirotaksane (polyrotaxanes) met komplekse molekulêre argitektuur bestudeer. Daar is bewys dat AF4 uitsluitlik gebruik kan word as ‘n meer geskikte tegniek bo SEC. Baie hoër molekulêre massas kon deur middel van AF4 vir UHMM polibutadieenpolimere raakgesien word as gevolg van die verminderde afbrekende degradasie wat dikwels voorkom met SEC. Jel-bevattende spesies is suksesvol geïdentifiseer met behulp van AF4 waartydens geen filtrering vir analise nodig was nie. Abnormale retensie was sigbaar tydens SEC analise van monsters van polirotaksane, wat dikwels voorkom in vertakte polimere. In teenstelling het AF4 bewys dat ‘n bevredigende skeiding van klein na groot molekulêre massas, sonder enige tekortkominge, moontlik is.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In the modern, fast moving society of today, there is a strong focus in research placed on the elimination of lengthy invasive medical procedures. Target specific, and chemo selective treatments are of great interest. Various advantages of this include patient comfort and over and above all cost reduction of invasive procedures. This project focused on the development of an injectable gel system with the use of biocompatible polymers. A system is regarded as injectable if the functional polymers are in solution before administration, but gels when added together. In order to design this system, one has to make use of polymers with complimentary functional groups. Telechelic amino-functionalized PVP with narrow molecular weight distribution was synthesized via RAFT-mediated polymerization. The polymer was thoroughly characterized and cross-linked with Poly(styrene-alt-maleic anhydride) to form a three dimensional polymeric network capable of absorbing and retaining large amounts of water and or biological fluid. Unfortunately the cross-linking needed to be performed in non-aqueous solution due to hydrolysis of maleic anhydride as a competing reaction in water. The gel was used in two model studies. The first model study focused on the attachment of a synthetic polypeptide onto the gel. The second model study evaluated the cytotoxicity effects of these gels when placed in direct contact with rodent cardiac myoblast and myocyte cells. These studies rendered promising results for future biological applications. / AFRIKAANSE OPSOMMING: In die moderne, vinnig bewegende samelewing van vandag, word daar in navorsing, 'n sterk fokus geplaas op die uitskakeling van lang indringende mediese prosedures. Doel spesifieke, en chemo selektiewe behandelings is van groot belang. Verskeie voordele van hierdie is die toename in gemak van die pasiënt en die verlaging van kostes verbonde aan hierdie indringende prosedures. Hierdie projek het gefokus op die ontwikkeling van 'n inspuitbare gel stelsel deur gebruik te maak van biologiese aanvaarbare polimere. ‘n Stelsel word beskou as inspuitbaar, indien die funksionele polimere in oplossing is voor toediening, maar wel kan gel wanneer bymekaar gevoeg word. Om hierdie tipe stelsel te kan ontwerp moet daar gebruik gemaak word van polimere met beskikbare funksionele groepe. Telecheliese amino-funksionele Poly(N-vinielpirollideen) met 'n smal molekulêre gewig verspreiding is gesintetiseer deur middel van RAFT-bemiddelde polimerisasie. Die polimeer is deeglik gekarakteriseer en daarna gekruis-koppel met P(STY-alt-MAnh) om 'n driedimensionele polimeriese netwerk te vorm. Hierdie netwerk is dan ook in staat om groot hoeveelhede water en/of biologiese vloeistof te absorbeer en te behou. Ongelukkig was hierdie reaksie uitgevoer in ʼn nie-waterige oplossing as gevolg van die hidrolise van Maleïne anhydride as 'n mededingende reaksie in water. Die gel is in twee model studies gebruik. Die eerste model-studie het gefokus op die beslaglegging van 'n sintetiese polipeptied op die gel. Die tweede model studie het die sitotoksiese uitwerking van hierdie gels in direkte kontak met knaagdier hart myoblast en lymfocyten selle geëvalueer. Hierdie studies het dan ook belowende resultate vir toekomstige biologiese toepassings gelewer.

Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2008. / In this study the coordination of ligands with several coordination sites, 2-aminoazoles (2- amino-4-methylthiazole), 2-aminobenzothiazole, 2-aminobenzoimidazole and 2- aminothiazoline and a biguanidine (N-(2-methylphenyl)imidodicarbonimidic diamide) to soft metal centres [gold(I) (group 11), chromium(0) (group 6) and tungsten (0) (group 6)] was investigated. The aminoazoles have three coordination sites, an exocyclic amine nitrogen, an endocyclic imine nitrogen and an endocyclic thioether sulphur. The biguanidine ligand has three sites for deprotonation, one central amine and two imine nitrogens, and at least five sites available for nitrogen coordination.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study involved the analysis of crystallization kinetics by means of a unique and newly developed Solution crystallization analysis by laser light scattering (Scalls) technique. In the main study we compared two commercial linear low-density polyethylene (LLDPE) polymers (PE-1- octene and PE-1-hexene) and studied the effect of short-chain branching on the solution crystallization of these complex polymer systems. Characterization of the polymers was done by nuclear magnetic resonance spectroscopy (NMR) and high-temperature gel permeation chromatography (HT-GPC). The second study involved the fractionation of a PE-1-hexene copolymer by temperature rising elution fractionation (Tref) and analyzing the solution crystallization of the different temperature fractions. This resulted in important details on the different molecular regions present in the polymer. A third additional study was done on the compatibility in polyolefin blends. Two different blends were prepared: isotactic polypropylene (iPP) – low density polyethylene (LDPE) blend and iPP – polypropylene impact copolymer (PPIC) blend. It was found that co-crystallization only occurred for the iPP - PPIC blends. Phase separation occurred for the iPP – LDPE blends, resulting in the formation of two phases for all blend compositions. Solution crystallization analysis is usually measured by the conventional Crystallization Analysis Fractionation (Crystaf) technique. In this study all crystallization data were compared with Crystaf results and a good correlation was found between the results obtained by Crystaf and Scalls. The major advantages of the Scalls technique are that, results similar to that of Crystaf can be acquired with much shorter analysis times and Scalls also allows for the measurement of solution melting of the crystallized polymer solutions. / AFRIKAANSE OPSOMMING: Hierdie studie het die analise van kristallisasie kinetika behels met behulp van die unieke en nuut ontwikkelde oplossing kristallisasie analise deur laser lig verstrooiing (Scalls) tegniek. In die hoof studie het ons twee kommersïele liniêre lae-digtheid polietileen (LLDPE) polimere (PE-1-okteen en PE-1-hekseen) vergelyk en die effek van kort-ketting vertakking op kristallisasie in oplossing van hierdie komplekse polimeer sisteme bestudeer. Karakterisering van die polimere was gedoen met kern magnetiese resonans spektroskopie (KMR) en hoë-temperatuur gel permeasie kromatografie (HT-GPC). Die tweede studie het die fraksionering van ‘n PE-1-hekseen ko-polieer met behulp van temperatuurstyging eluering fraksionering (Tref) behels asook die analisering van kristallisasie in oplossing van die verskillende temperatuur fraksies. Belangrike informasie oor die verskillende molekulêre areas teenwoordig in die polimeer was verkry. ‘n Derde addisionele studie was gedoen op die versoenbaarheid in poliolefin mengsels. Twee verskillende mengsels was voorberei: isotaktiese polipropileen (iPP) – lae digtheid polietileen (LDPE) mengsel en iPP – polipropileen impak ko-polimeer (PPIC) mengsel. Daar was gevind dat ko-kristallisasie slegs in die iPP – PPIC mengsel plaasgevind het. Fase skeiding het plaasgevind in die iPP – LDPE mengsels wat tot twee fases gelei het vir alle mengsel komposisies. Kristallisasie in oplossing word gewoonlik gemeet met die konvensionele kristallisasie analise fraksionering (Crystaf) tegniek. In hierdie studie was al die kristallisasie data met Crystaf resultate vergelyk en ‘n goeie korrelasie was gevind tussen die resultate van Crystaf en Scalls. Die grootste voordele van die Scalls tegniek is dat resultate soortgelyk aan diè van Crystaf kan verkry word met baie korter analises en Scalls laat ook toe vir die meting van smeltpunt van die gekristalliseerde polimeer oplossings.

Thesis (MSc)--Stellenbosch University, 2012. / Please refer to full text for abstract

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Dithiadiazolyl heterocyclic radicals form part of an ever-growing research field in the quest for organic magnets and conducting materials due to the lone electron located within the heterocyclic ring. These compounds could potentially be used as electrical current conductors and transistors which may be developed into a molecular switch or other types of molecular devices. This thesis describes the successful synthesis of three nitrile functionalised calix[4]arenes, mono-, distal- and tetra-, as bulky scaffolds to be used as precursors in the synthesis of dithiadiazolyl functionalised calix[4]arenes. The crystal structures of these three nitriles are reported herein for the first time. Dithiadiazolyls tend to dimerise in the solid state, thus by selecting a calix[4]arene as a bulky R-group, it was hoped to inhibit dimerisation. Furthermore, synthesis of the radicals on different positions of the calix[4]arene may also inhibit dimerisation in the solid state. The typical reaction in the synthesis of dithiadiazolyls involves the reaction between a nitrile and lithium bis(trimethylsilyl)amide followed by the formation of the dithiadiazolylium chloride salt by the addition of sulfur dichloride. The salt is subsequently reduced giving the desired dithiadiazolyl. However, the addition of lithium bis(trimethylsilyl)amide to mono-nitrile calix[4]arene in the synthesis of the mono-dithiadiazolyl functionalised calix[4]arene was unsuccessful. To investigate the incompatible nature of the electrophile and nucleophile, computational and physical experiments were conducted on the mono-nitrile calix[4]arene derivative. These avenues were pursued to determine whether the unreactive nature of the nitrile in this case is due to electronic effects. Changes in the reaction conditions (i.e. temperature, solvent and the equivalents of nucleophile) were all varied, but this proved to be unsuccessful. Computationally, through charge calculations, it was determined that the electronic properties of the nitrile were similar to that of nitrile examples known to work in the literature. Therefore, it was established that steric effects of the calix[4]arene are playing a critical role in the unreactive nature of the nitrile. There are two non-degenerate LUMO orbitals for the nitrile as one is conjugated and the other is planar (LUMO + 1) to the aromatic system. It has been established that nucleophilic attack through the lowest energy LUMO would result in a high energy transition state due to the loss of conjugation and attack through the higher energy LUMO + 1 would result in a lower energy transition state. However, this was not possible due to the steric conditions surrounding its position relative to the nitrile. The results obtained from this study were, therefore, able to confirm that the normally suitable reaction procedure seems to be limited to less sterically encumbered nitriles. / AFRIKAANSE OPSOMMING: Dithiadiazolyl heterosikliese radikale vorm deel van 'n steeds groeiende navorsingsveld in die soeke na organiese magnete en material met geleidingsvermoë as gevolg van die ongepaarde elektron wat binne in die heterosikliese ring geleë is. Hierdie verbindings kan moontlik gebruik word as elektriese stroom geleiers en transistors wat tot 'n molekulêre skakelaar of ander tipe molekulêre toestelle ontwikkel kan word. Hierdie tesis beskryf die suksesvolle sintese van drie nitriel gefunksionaliseerde calix[4]arene, mono-, distale- en tetra-, as lywige steiers om as voorgangers in die sintese van dithiadiazolyl gefunksionaliseerde calix[4]arene gebruik te word. Die kristal strukture van hierdie drie nitriele is hier in vir die eerste keer gerapporteer. Dithiadiazolyls is geneig om te dimeriseer in die vaste toestand. Daarom is die redenasie agter die keuse van die calix[4]arene as 'n lywige R-groep, as dimeriseering te inhibeer. Sintese van die radikale op verskillende posisies van die calix[4]arene kan dimeriseering in die vaste toestand inhibeer. Die tipiese reaksie in die sintese van dithiadiazolyls behels die reaksie tussen 'n nitriel en litium bis(trimetielsiliel)amied gevolg deur die vorming van die dithiadiazolylium chloried sout deur die byvoeging van swaeldichloried. Die sout is dan gereduseer om die gewenste dithiadiazolyl te vorm. Die toevoeging van litium bis(trimethielsiliel)amied mono-nitriel calix[4]arene in die sintese van die mono-dithiadiazolyl calix[4]arene was egter onsuksesvol. Om die oënskynlik onverenigbare aard van die electrofiel en nukleofiel te ondersoek, is rekenaar-berekeninge en fisiese eksperimente uitgevoer op die mono-nitriel calix[4]arene afgeleide. Hierdie twee maniere is gevolg om te bepaal of die onreaktiewe aard van die nitriel in hierdie geval as gevolg van elektroniese effekte is. Wysigings in die reaksie omstandighede (d.w.s. temperatuur, oplosmiddel en die ekwivalente van nukleofiel) is gemaak, maar dit was onsuksesvol. Deur middle van ladings-berekeninge, is dit bepaal dat die elektroniese eienskappe van die nitriel soortgelyk is aan dié van nitriel voorbeelde wat in die literatuur geraporteer is. Daarom is dit vasgestel dat die steriese effekte van die calix[4]arene 'n kritieke rol in die onreaktiewe aard van die nitrile speel. Daar is nie-ontaarde LUMO orbitale vir die nitriel soos 'n mens is vervoeg en die ander is planêr (LUMO + 1) na die aromatiese stelsel. Daar is vasgestel dat nukleofieliese aanval deur die laagste energie LUMO sal lei tot 'n hoë energie oorgangstoestand as gevolg van die verlies van konjugasie. Aanval deur die hoër energie LUMO + 1 sou lei tot 'n laer energie oorgangstoestand. Dit was egter nie moontlik nie, as gevolg van die steries toestande rondom die orbital se posisie met betrekking tot die nitriel. Die resultate van hierdie studie bevestig, dus, dat die gewone reaksie proses beperk is tot minder steries verhinderde nitriele.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Inclusion and porosity properties of the following supramolecular solid-state hosts were investigated: • 2,7-dimethylocta-3,5-diyne-2,7-diol • 2-methyl-6-phenylhexa-3,5-diyn-2-ol • Dianin’s compound • p-tert-butyl-calix[4]arene • 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetramethoxy-2,8,14,20- tetrathiacalix[4]arene • Two discrete coordination metallocycles, [Ag2IMID2](BF4)2 and [Cu2(BITMB)2(Cl)4] All of these compounds form well-defined crystalline host structures. Inclusion phenomena involving encapsulation of liquids were studied using single-crystal x-ray diffraction methods. Several guest-free host structures (α phases) were structurally elucidated and their gas sorption properties were investigated. Studies of the sorption properties of seemingly nonporous materials were carried out to provide insight into this rare phenomenon. Water and iodine sorption by a polymorph of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetramethoxy-2,8,14,20- tetrathiacalix[4]arene shows that the conventional perception of sorption through the solid-state requires reassessment. Gas sorption studies were carried out using apparatus devised and presented here. These include sorption apparatus and a device to determine single-crystal structures under controlled gas atmospheres.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / In a Fischer-Tropsch refinery environment carboxylate complexes are of interest since the carboxylic acids present in product streams lead to formation of carboxylate salts through leaching of process equipment and catalysts. It is widely accepted that decomposition of organic (carboxylic) acids catalysed by metals is controlled by the decomposition of metal salts or complexes previously formed with such an acid. The determination of physical and structural properties of caboxylate complexes could contribute to the explanation of the mechanism involved in the decarboxylation of carboxylic acids. We have successfully determined the molecular structures of copper(II) allyl acetate, zinc(II) formiate, zinc(II) isovaleroate, yttrium(III) acetate and lanthanum(III) propionate. It has been established that zinc has a preferred tetrahedral coordination in carboxylate complexes compared to the octahedral coordination of copper, lanthanum and yttrium complexes considered. The carboxylate O-C-O angle in these complexes range between 119° and 125° and the conformation of the carbon chains is anti in all cases except for copper(II) allyl acetate, where a gauche conformation is adopted. Using structural methods such as TGA, infrared spectroscopy and X-Ray powder diffraction and combining it with existing knowledge of yttrium carboxylates and the effective use of computational chemistry – to calculate favourable internal parameters, using DFT calculations and B-LYP level theory - a likely structure for yttrium(III) propionate is proposed. The use of infrared measurements were especially valuable towards predictions of possible structures and the postulations of Nakamoto, on the relation between carboxylate carbonyl stretching frequencies and the nature of the carboxylate bond, could be used to accurately identify – except for the formiate salts of zinc(II) and yttrium(III) – the bonding mode present in the relevant compounds. We systematically tuned the non-cyclic organic part of the mono carboxylate ligand by lengthening and branching of the alkyl chain and determined that thermal decomposition and heat capacity of zinc complexes are a strong function of the ligand, while the behaviour of analogous yttrium complexes is hardly affected. The thermal investigation of lanthanum(III) propionate yielded a result that is in contrast with a previous study - where only CO2 was reported as byproduct - and we report an alternative result which indicates formation of symmetric ketones when the compound is heated to a high enough temperature. Earlier general assumptions about the layer-like crystal structure of lanthanum complexes coordinated by alkyl chain carboxylate are contradicted by the crystallographic data we collected for this compound. The crystal packing of lanthanum(III) propionate clearly shows a layered structure which is unexpected for a carboxylate with such a short alkyl.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / In papermaking, the addition of filler can be detrimental to the properties of the resulting paper hence the use of additives that enhance paper properties are of paramount importance. Syndiotacticity rich poly(vinyl alcohol) (PVA) microfibrils were prepared for use as filler retention aids. They were prepared via in situ fibrillation during the saponification of high molecular weight poly(vinyl pivalate). The resulting fibers had high thermal stability and crystalline melting temperature. They were not fully soluble in water even at 100 oC. In order to make them less water resistant the syndiotacticity of the PVA microfibrils was varied by copolymerizing vinyl pivalate with vinyl acetate and saponifying the resultant copolymer. It was observed that changes in syndiotacticity had a significant effect on the crystallinity, morphology and thermal properties of the resultant PVA. The surfaces of the fibers were modified by first crosslinking using glyoxal (a dialdehyde), and then attaching cationic and anionic groups by grafting and by carboxymethylation. Crosslinking prior to modification was beneficial in minimizing the solubility of the fibers in the aqueous media in which they were modified. Heterogeneous modification techniques were employed so that fiber properties could be preserved. Carboxymethylation was carried out using the two step Williamson’s ether synthesis. The first step involves the formation of a highly reactive alkoxide by the reaction of PVA with a strong base and the second its etherification using a functional alkyl halide. Poly(methacryloyloxy ethyl trimethyl ammonium chloride) and poly(acrylic acid) were grafted from the PVA microfibrils using the KPS/Na2S2O3 redox initiation system. Grafting was confirmed by FTIR and NMR spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were carried out on both modified and unmodified PVA microfibrils. The results showed that crosslinking resulted in an enhancement of the thermal properties of the microfibrils. A decline in the onset temperature for thermal degradation and crystalline melting temperature were observed, and were attributed to the modification of the PVA microfibrils.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / Hybrid graft copolymers of polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA) were synthesised. PDMS macromonomers were synthesised anionically from the cyclic D3 monomer. This living polymerisation was terminated with a [3- (methacryloxy)propyl]-dimethylchlorosilane terminating agent which resulted in the functionalised macromonomer. These PDMS macromonomers and MMA monomer were copolymerised to form PMMA-g-PDMS hybrid copolymers by conventional free radical reactions. Synthesised and commercial methacryloxy-functionalised PDMS macromonomers having a range of molar masses were copolymerised with MMA to form graft copolymers of various chemical compositions. PDMS content in the graft copolymers could be varied by the amount of PDMS incorporated into the copolymer as well as by varying the length of the PDMS side chains. Size exclusion chromatography (SEC) results confirmed low PDI’s for the PDMS macromonomers synthesised anionically. NMR studies allowed characterisation of the synthesised PDMS macromonomers and PMMA-g-PDMS copolymers. It also allowed the determination of relative ratios of PMMA:PDMS in the graft copolymers. Gradient elution chromatography (GEC) was used successfully to monitor the presence and removal of the PDMS macromonomer from the graft copolymer products. The influence of PDMS content of the graft copolymers on retention time was also evaluated using this technique. Two dimensional chromatography confirmed the formation of PMMA-g-PDMS copolymer as well as PMMA homopolymer during some of the grafting reactions. GEC in the first dimension was coupled to SEC in the second dimension. PAS-FTIR studies allowed chemical characterisation of the graft copolymer and confirmed surface segregation of the PDMS. Atomic force microscopy (AFM) was also used to study the surface segregation of PDMS and looked at the relationship between surface polarity and increasing PDMS content. The study showed the effect of thermal treatment on the surface morphology of the hybrid polymers. Corona treatment was used to modify the surface structure of the graft copolymer films. Contact angle studies provided evidence of hydrophobic loss and recovery after corona for the hybrid polymer materials containing PDMS. This is one of the first reported examples of hydrophobicity recovery in these types of hybrid materials after corona treatment. Slow positron beam studies highlighted the formation of a thin silica like layer on the surface of the films after corona similar to that observed for pure cross-linked PDMS compounds. The positron studies enabled estimation of the thickness of the silica like layer.