This study concerned the synthesis of modified terephthalic acid monomers and branched dialcohols for the synthesis of polyesters with different properties. Monomers were prepared by esterification of terephthalic acid (TPA) and the alkylation of the ester dimethyl terephthalate (DMT). If alkylation was unsucessful, TPA was brominated using N-bromosuccinimide (NBS) and other brominating agents. However, the bromination reactions were also unsuccessful. Therefore, oxidation reactions of 2-bromoparaxylene were conducted as an attempt to obtain the desired monomers, however a mixture of products was produced that were difficult to separate. Subsequently, the brominated TPA was bought, and the alkylation reactions were performed using tetramethyltin and other alkylating agents; however the alkylation reaction was once again unsuccessful. Despite the difficulties encountered during monomer synthesis, polymerization of the obtained monomers was investigated. Polymer synthesised by the technique of condensation polymerization of branched diols and the brominated TPA. The unbranched diol monomers and unsubstituted DMT were used to synthesize reference polymers for comparison with the novel polymers produced in this study. The following diols were used: 1,2-propanediol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol. A batch reactor equipped with a mechanical stirrer connected to the vacuum pump was used as polymerization vessel. The polyesters were synthesised and they were characterised using IR and NMR. Additional polymer analysis was performed using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Gel permeation Chromatography (GPC) and Scanning Electron Microscopy (SEM). The results of the analyses indicated that the polymers became flexible and softer with an increasing number of methylene units in the main chain. Consequently, the melting point of the polymer decreased when there was branching present. SEM analyses showed that polymers were softer and had no hard edges, and the SEM also showed the catalyst inside the polymers. The decomposition temperature changed very slightly with alkyl substitution or the presence of bromide in benzene ring. It was concluded that the benzene ring did not become activated as a number of methods were attempted unsuccessfully to facilitate reaction by either alkylation or bromination. The methyl branches on the diols were not held responsible for any changes in the properties of the polyesters. Bromination of the monomers resulted in polymers that were structurally amorphous and that demonstrated a low tensile strength. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015

This study concerned the synthesis of modified terephthalic acid monomers and branched dialcohols for the synthesis of polyesters with different properties. Monomers were prepared by esterification of terephthalic acid (TPA) and the alkylation of the ester dimethyl terephthalate (DMT). If alkylation was unsucessful, TPA was brominated using N-bromosuccinimide (NBS) and other brominating agents. However, the bromination reactions were also unsuccessful. Therefore, oxidation reactions of 2-bromoparaxylene were conducted as an attempt to obtain the desired monomers, however a mixture of products was produced that were difficult to separate. Subsequently, the brominated TPA was bought, and the alkylation reactions were performed using tetramethyltin and other alkylating agents; however the alkylation reaction was once again unsuccessful. Despite the difficulties encountered during monomer synthesis, polymerization of the obtained monomers was investigated. Polymer synthesised by the technique of condensation polymerization of branched diols and the brominated TPA. The unbranched diol monomers and unsubstituted DMT were used to synthesize reference polymers for comparison with the novel polymers produced in this study. The following diols were used: 1,2-propanediol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol. A batch reactor equipped with a mechanical stirrer connected to the vacuum pump was used as polymerization vessel. The polyesters were synthesised and they were characterised using IR and NMR. Additional polymer analysis was performed using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Gel permeation Chromatography (GPC) and Scanning Electron Microscopy (SEM). The results of the analyses indicated that the polymers became flexible and softer with an increasing number of methylene units in the main chain. Consequently, the melting point of the polymer decreased when there was branching present. SEM analyses showed that polymers were softer and had no hard edges, and the SEM also showed the catalyst inside the polymers. The decomposition temperature changed very slightly with alkyl substitution or the presence of bromide in benzene ring. It was concluded that the benzene ring did not become activated as a number of methods were attempted unsuccessfully to facilitate reaction by either alkylation or bromination. The methyl branches on the diols were not held responsible for any changes in the properties of the polyesters. Bromination of the monomers resulted in polymers that were structurally amorphous and that demonstrated a low tensile strength. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015

A series of new, well-defined poly(ether ether sulfone), poly(ether ether ketone) and polyimide derivatives containing the diphenylethylene moiety were prepared by step-growth polymerization methods. Poly(ether ether sulfone) derivatives were prepared by two step-growth polymerization methods: (a) The cesium fluoride catalyzed polycondensation reactions of 4,4´-difluorodiphenylsulfone with different mole percentage ratios of silylated bisphenol derivatives, 2,2-bis(4-tbutyldimethylsiloxyphenyl) propane and 1,1-bis(4-t-butyldimethylsiloxyphenyl)ethylene in N-methyl-2-pyrrolidone at 150 °C. (b) The potassium carbonate catalyzed nucleophilic aromatic substitution polycondensation reactions of 4,4´-difluorodiphenylsulfone with different mole percentage ratios of bisphenol A and 1,1-bis(4-hydroxyphenyl)ethylene in N,N-dimethylacetamide and toluene at 165 °C. Poly(ether ether ketone) derivatives were prepared by the cesium fluoride catalyzed polymerization reactions of 4,4´-difluorobenzophenone with different mole percentage ratios of 2,2-bis(4-t-butyldimethylsiloxyphenyl)propane and 1,1-bis[4-(t-butyldimethylsiloxy)- phenyl]ethylene in N-methyl-2-pyrrolidone at 150 °C. Polyimide derivatives were prepared by step-growth polymerization methods by the polycondensation reactions of 4,4´-oxydiphthalic anhydride with different mole percentage ratios of 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 1,1-bis(4-aminophenyl)ethylene. The intermediate polyamic acids were subjected to thermal imidization processes to provide the corresponding polyimide derivatives. Due to the regiospecific introduction of the 1,1-diphenylethylene group along the polymer backbone, the different poly(ether ether sulfone), poly(ether ether ketone) and polyimide derivatives were subjected to post-polymerization sulfonation reactions via the thiol-ene reaction using sodium 3-mercapto-1-propane sulfonate as sulfonating agent and AIBN as initiator in N-methyl-2-pyrrolidone/dimethylsulfoxide at 75 °C for 5 days. The 1,1- diphenylethylene derivatives and the different polymeric compounds were characterized by size exclusion chromatography, dilute solution viscometry, 1H NMR and 13C NMR spectrometry, FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, atomic force microscopy, transmission electron microscopy, elemental analysis, energy dispersive spectroscopy and ion exchange capacity measurements. / Chemistry / M.Sc.(Chemistry)

Dissertation (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The kinetics of drying and film formation of different polymeric latices were studied. Various theoretical models predict a strong dependency of the film formation characteristics on the particle size and morphology. This could be confirmed by experimental studies. The influence of particle size and morphology of differently structured latices on the film formation process was investigated by Atomic Force Microscopy (AFM) and Ultrasonic shear wave reflection. These two methods allow a comprehensive characterization of the drying and film formation process of emulsions. The studies confirmed the theoretical model, that the film formation behavior is influenced by the particle size and particle morphology. Furthermore the influence of different additives, such as coalescent solvents and rheology modifiers on the film formation behavior was investigated. As a second part of the studies, a novel technique was developed to measure thermal transitions of polymers with the AFM in the non-contact mode, using it as a Dynamic Mechanical Analyzer (DMA) on a local scale. The resonance frequency of the AFM cantilever was measured as a function of the temperature and thermal transitions of a polymer were clearly visible as changes in the resonance frequency / temperature response curve. Using the AFM in this mode allows the determination of the thermal properties of a material at a specific position on a sample, thereof on a macromolecular scale. A simple model was developed to explain the response of the cantilever caused by the transitions in the polymer and the related form of the frequency/temperature curves. This new technique adds a new dimension to standard thermal analysis techniques. It is now possible to resolve the individual thermal transitions of different polymer phases, for example in structured multiphase polymers. / AFRIKAANSE OPSOMMING: Die kinetika van droging en filmvorming van verskeie polimeriese lateksverbindingse is ondersoek. Verskeie teoretiese modelle voorspel 'n sterk afhanklikheid tussen die filmvormingseienskappe, partikelgrootte en morfologie. Hierdie afhanklikhede is eksperimenteel bevestig. Die invloed van partikelgrootte en morfologie van verskillende lateksstrukture op die filmvormingsproses is deur atoominteraksiemikroskopie (Eng: Atomic Force Microscopy, AFM) sowel as ultrasoniese skuifweerstandgolfrefleksie ondersoek. Hierdie twee metodes bied 'n deurslaggewende karakterisering van die droging en filmvormingsproses van emulsies. Resultate bevestig die teoretiese model, nl. dat filmvorming deur partikelgrootte en morfologie beïnvloed word. Die invloed van verskillende bymiddels, insluitend reologie-modifiseerders op filmvorming, is ook ondersoek. Vervolgens is 'n nuwe tegniek ondersoek om die termiese oorgange van polimere met behulp van die AFM in nie-kontak modus (deur dit as 'n dinamiese meganiese analiseerder (DMA) te gebruik) te bestudeer. Die resonansie-frekwensie van die AFM-hefboom is bepaal as 'n funksie van temperatuur. Termiese oorgange van 'npolimeer is duidelik waarneembaar as veranderinge in die resonansfrekwensie/ temperatuur responskurwe. Deur gebruik te maak van die AFM in hierdie modus kan die termiese eienskappe van 'n materiaal by 'n spesifieke posisie op die monster op molekulêre skaal bepaal word. 'n Eenvoudige model is ontwikkel om die oorgange in die polimeer, en gevolglik die vorm van die frekwensie/temperatuur kurwes, dmv. die respons van die hefboom, te verduidelik Hierdie nuwe tegniek gee 'n nuwe dimensie tot die standaard tegnieke van termiese analise tegnieke. Dit is nou moontlik om individuele termiese oorgange van verskeie polimeerfases, byvoorbeeld in gestruktureerde multifase polimere, te ondersoek en op te los

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The study presented in this dissertation had as primary aim to develop pathways to heterogeneous aqueous polymerizations that had living characteristics. To this end, the reversible addition fragmentation chain transfer (RAFT) process was investigated in predispersed and ab initio emulsions as well as homogeneous media. The synthesis of RAFT agents was carried out. The compounds prepared provided varied behaviour in reaction. In situ IH nuclear magnetic resonance (NMR) increased understanding of homogeneous RAFT mediated polymerizations. The early behaviour of RAFT mediated polymerizations led to the definition of initialization; a period before pre-equilibrium in a polymerization where degenerate behaviour occurs. Stable miniemulsion preparation methods were developed that provided living polymer latexes using high surfactant concentrations. The effect of surfactant concentration on particle size and latex stability was investigated. Living polymer characteristics were shown by the use of size exclusion chromatography, and 2- dimensional chromatography conclusively showed block polymer formation. In situ NMR spectroscopy of emulsions in deuterated water was used to provide evidence on the role of initiator solubility in polymerization. Secondary nucleation in high surfactant concentration miniemulsions systems was investigated using both particle size and molar mass analysis techniques and a means of eliminating secondary particle nulceation was shown through the use of aqueous phase radical traps. The role of the RAFT agent used in the polymerization was shown to be significant in determining the extent to which multiple polymer distributions formed in the polymerization in that radical exit from particles was affected. Finally, a new form of emulsion polymerization, which has been termed proto-seeded emulsion, has been developed. The proto-seed latex is formed by using a monomer whose polymer has chain length dependent water solubility. This process allows ab initio RAFT mediated emulsion polymerization to be conducted successfully without transport of RAFT agents in heterogeneous media. / AFRIKAANSE OPSOMMING: Die primerê doel in hierdie dissertasie is die ontwikkeling van roetes na heterogene water-gebaseerde polimerisasies met lewende eienskappe. Om hierdie doel te bereik is die omkeerbare addisie fragmentasie ketting oordrag proses (eng reversible addition fragmentation chain transfer (RAFT)) ondersoek in vooraf verspreide en direkte emulsies sowel as homogene media. Die sintese van RAFT agente is uitgevoer. Die verbindings wat voorberei is het verskillende einskappe in reaksies getoon. In situ IH kern magnetiese resonansie (KMR) het die kennis en begrip van homogene RAFT polimerisasies uitgebrei. Die vroeë gedrag van RAFT polimerisasies het tot die definisie van inisialisasie gelei; 'n periode voor die pre-ekwilibrium in 'n polimerisasie waartydens "degenerate" gedrag plaasvind. Stabiele miniemulsie voorbereidings metodes is ontwikkel wat lewende polimeer latekse verskaf het met gebruik van hoë seep konsentrasies. Die effek van seep konsentrasie op partikel grootte en lateks stabilitiet is ondersoek. Lewende polimeer eienskappe is bewys deur gebruik te maak van grootte-uitsluiting vloeistof chromatografie, en 2-dimensionele chromatografie het duidelik blok-polimeer vorming gewys. In situ KMR spektroskopie van emulsies in gedeutereerde water is gebruik om bewys te lewer van die rol van initieerder-oplosbaarheid in polimerisasie. Sekondêre nukleasie in hoë seep konsentrasie miniemuisie sisteme is ondersoek met die gebruik van beide partikel grootte sowel as molêre massa analise tegnieke. 'n Metode om sekondêre partikels te verhoed is verskaf deur gebruik te maak van waterfase radikaal lokvalle. Die rol van die RAFT agent in die polimeerisasie is beduidend in die graad van vorming van meer as een polimeer distribusie in die sin dat radikal uitgang van partikels beinvloed was. Ten slotte is 'n nuwe vorm van emulsie polimeerisasie ontwikkel wat proto-gesaaide emulsie genoem is. Die proto-gesaaide lateks is gevorm deur gebruik te maak van 'n monomeer waarvan die polimeer water-oplosbaarheid afhanklik is van die kettinglengte. Die proses laat ab initio RAFT emulsie polimerisasie toe om suksesvol uitgevoer te word sonder die vervoer van RAFT agente in heterogene media.

Thesis (M.Sc.)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: This thesis is a written record of an investigation into the self-assembly of organic monomers in amphiphilic solutions. The polymerizable surfactant sodium 10-undecenoate was used alone and with different concentrations of styrene and methyl methacrylate monomers and phenyl acetophenone initiator to investigate single particle formation from a simple amphiphilic self-assembly. Reactions were carried out under either ultra-violet light or gamma irradiation. It was shown that copolymerization between the surfactant and the monomers did not occur to any significant extent. This meant that inclusion of easily modifiable carboxyl functionalities in the polymer by incorporation of the carboxylate surfactant could not be quantified. Star-like particles were found. The shape of the particles formed, was the result of surfactant self-assembly to create self-assembled particles rather than templating of polymeric material. Polymerization of the unsaturated surfactant particles occurred to low conversions only. Analyses of formed particles were carried out using scanning electron microscopy, transmission electron microscopy, atomic force microscopy, field emission scanning electron microscopy and light microscopy for structure observation. The techniques of energy dispersive analysis by x-rays, particle SIze analysis, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared analysis, nuclear magnetic resonance, small angle x-ray scattering and inductively coupled plasma (for counter-ion analysis) were used for the gathering of physical data. / AFRIKAANSE OPSOMMING: Hierdie studie is 'n geskrewe rekord van 'n ondersoek van die self-aneensetting van organiese monomere in amfifiliese oplossings. In die ondersoek is die polimeeriseerbare seep natrium 10-undekenoaat alleen en saam met verskillende konsentrasies van monomere en feniel asetofenoon gebruik om enkelpartikel formasie vanaf 'n eenvoudige amfifiliese templaat te ondersoek. Reaksies is uitgevoer onder of ultra-violet lig, of gamma bestraling. Dit is bewys dat kopolimerisasie tussen die seep en die monomere me III emge merkwaardige hoeveelhede plaasgevind het nie. Dit beteken dat insluiting van maklik veranderbare karboksiel funksionele groepe in die polimeer deur middel van insluiting van die karboksilaat seep nie meetbaar was nie. Ster-vormige partikels is gevind. Dit is getoon dat die vorm van die partikels wat in die vroeëre werk verkry is, die resultaat van seep self-aaneensetting, eerder as templatering van polimeriese materiaal is. Polimerisasie van die seep partikels het net tot lae vlak van omskakeling plaasgevind. Analise van die gevormde partikels is uitgevoer deur middel van skandeer elektron mikroskopie; transmissie elektronmikroskopie; atomiese kragmikroskopie; veldemissie skandeer elektron mieroskopie en ligmikroskopie vir struktuur bepalings. Die tegnieke van energie dispersie analiese deur middel van x-strale; deeltjie grootte analise; differensiaal skandeer kalorimetrie; termogravimetriese analise; Fourier transformasie infra rooi analiese; kern magnetiese resonansie; klein hoek x-straal diffraksie en induktief-gekoppelde plasma (vir teenioon analise) is gebruik om fisiese data te versamel.

Monomers and polymers containing the quinodimethane unit were synthesized. The infrared, nuclear magnetic resonance (NMR) and ultraviolet spectra of these materials were also reported. Oxidation of the enolate dianoion of α, α'-di(carbomethoxy)-α, α'-diphenylquinodimethane (DMPQH₂) with iodine gave 7,8-di(carbomethoxy)-7,8-diphenylguinodimethane (DMPQ) in greater than 50% yield. This compound had a reduction potential of -0.85V (Ag/AgCl reference) but would not form charge transfer complexes with electron donors. Attempted polymerization reactions of DMPQ were also discussed. A series of donor - acceptor substituted quinodimethanes was synthesized and a discussion of their electronic properties was included. Condensation copolyesterification of two of these materials was performed. Polymers with inherent viscosities ranging from 0.11 dL/g to 0.45 dL/g were obtained. The polymers were soluble at room temperature in hexafluoroisopropanol (HFIP) and a 1 : 1 solution of phenol/chlorobenzene. The polymers were also soluble at elevated temperatures in dipolar aprotic solvents.

M.Sc. / Polymerization of a-olefins by metallocene-based catalysts, is an ever expanding field with current scientific research continuing in an endeavor to develop chiral catalysts with greater stereospecificity and activities. However, the application of metallocene catalysts in oligomerization reactions of a-olefins has been somewhat neglected. This is despite the fact that metallocene catalysis can offer a convenient route to the synthesis of higher a-olefin oligomers. Furthermore, by utilizing an assortment of functional group transformations, a-olefin oligomers can serve as intermediates for a variety of specialty chemicals. Notwithstanding the possibility of employing alternative ligands in catalysis, the use of non-cyclopentadienyl-based complexes is a topic that has only recently been considered. Comparative studies of a series of analogous complexes is lacking in this field and thus a pertinent study of a number of known metallocene complexes was executed in this project. Furthermore, an industrially applicable process for oligomerization was sought after. This was in fact achieved by subjecting the a-olefins 1-pentene, 1- hexene and 1-octene, to oligomerization conditions with a previously unreported and lowered methylaluminoxane ratio. This reaction proved to be highly selective to dimer formation of the three aforementioned higher a-olefins. In order to gain more insight into the oligomerization process, the progress of the reaction was also followed. Only zirconium complexes were synthesized and furthermore, the induction of oligomerization as opposed to polymerization (using compounds known to be active solely as polymerization catalysts), was attempted by increasing the reaction temperature. The second part of this project entailed the synthesis and subsequent testing of zirconium catalysts containing non-cyclopenatadienyl-based ligands. These complexes have frameworks with chelating phenolate or naphtholate ligands. These complexes were tested for oligomerization, but results proved to be negative.

Orientador: Carlos Renato Zacharias / Banca: Ernesto Vieira Neto / Banca: Alvaro Jose Damião / Resumo: Este trabalho trata da simulação da ótica do olho humano, em especial a determinação do perfil de índices de refração do cristalino. Mostramos que a hipótese de índice de refração constante, para os meios óticos, não é adequada quando o objetivo é minimizar aberrações e se fazer um estudo da imagem formada na retina. Desenvolvemos um código computacional que utiliza a técnica do Traçado de Raio (ray tracing) acoplada a um processo de busca e otimização (recozimento simulado), visando determinar o perfil de variação dos índices de refração do cristalino, com a condição de minimização das aberrações. A parametrização do modelo foi baseada em resultados da Literatura e utilizamos faces asféricas (parabólicas). Para validar nosso modelo, comparamos nossos resultados com outros modelos existentes, e verificamos a qualidade da imagem formada na retina / Abstract: This work deals with the human eye optics simulation, focusing in the lens refraction index profile. We show that the hypothesis of constant refraction index, for the lens, is not adequate when the objective is minimize aberrations and to study the image formed in the retina. We developed a computational code that uses the ray tracing technique coupled to a search and optimization algorithm (simulated annealing), seeking to determine the profile of the refraction index for the crystalline lens that minimize the aberrations. The model's parametrization was based on Literature results and we implemented aspherical faces for the lenses. In order to validate our results, we compare with those in the Literature, and verify the image quality formed on the retina / Mestre

Thesis (Ph.D.) -- McMaster University, 2007. / Supervisor: Shiping Zhu. Includes bibliographical references.