Proton exchange membrane fuels cells (PEMFCs) are one of the primary alternatives to internal combustion engines. The key component is the proton exchange membrane, or PEM, which should meet a number of requirements, including good proton conductivity under partially humidified conditions. A number of alternative PEMs have been synthesized by copolymerizing various aromatic comonomers, but the smaller ion channels prohibit rapid proton transport under partially hydrated conditions. One solution has been to synthesize multiblock copolymers from hydrophilic and hydrophobic oligomers to ensure sufficient ion channel size. Four multiblock systems were synthesized from hydrophobic and hydrophilic oligomers and were characterized in this thesis. The first multiblock system incorporated a partially fluorinated monomer into the hydrophobic block, to improve phase separation and performance under partially humidified conditions. The second study was focused on phase separation and structure-property relationships as a function of casting conditions of a biphenol-based multiblock series. The third study featured a novel hydroquinone-based hydrophilic oligomer in the multiblock copolymer, which showed the promise of a higher ionic density, degree of phase separation and proton conductivity values. The fourth study in this thesis entailed the comparison of a block copolymer produced with two distinct synthetic routes: the multiblock synthesis from separate oligomers as previously published in the literature, and a segmented route seeking to achieve comparable structure-property relationships with the same monomers, but using a simpler synthetic route. The two block copolymer series were found to be comparable in their structure-property relationships. / Master of Science

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Polydimethylsiloxane–polyester (PDMS-PES) copolymers produce materials which have enhanced properties and take advantage of the unique properties of the two very dissimilar components. The dissimilar nature of the components results in these types of materials typically having complex morphologies in the solid state as a result of phase segregation. When the polyester component is crystallisable, an even richer variation in morphology can be expected. The chain structure of the copolymer in terms of the distribution of the various segments along the chain and the variation in the composition also has a dramatic impact on the solid state morphology. In this study, two different types of polyesters were used to synthesise five series of PDMS-PES segmented copolymers and one series of PDMS-PES branched copolymer. The two polyester segments selected were polybutyleneadipate (PBA) and polybuthylenecyclohexancarboxylate (PBCH). The copolymers were synthesised via polycondensation in the melt state. Insights on many variations in the PDMS-PES copolymer synthesis are given. The copolymer series synthesized gave systematic series where the influence of the polyester type, chain architecture, bulk composition, block length, crystallinity and processing condition on the bulk and surface morphology could be studied. The remarkable variations in the properties of the copolymer were attributed to the differences in the copolymers morphology in terms of the microphase segregation, crystallization and the free volume properties. These variations were also found to alter the nature of the surface compositions and the related surface properties. Multiphase morphology exhibited in all the PDMS-PES copolymers and the type of morphology observed was dependent on PDMS contents, PDMS segment length and the degree of branching. Three types of morphology were observed: spherical micro-domains of PDMS in a matrix of PES, bicontinuous double diamond type morphology, and spherical micro-domains of PES in a matrix of PDMS. Spherical domains of the PDMS were also observed for low PDMS content copolymers between the crystalline polyester lamellae. The complexity of the PDMS-PBCH copolymer morphology was further investigated, using an extensive set of experimental data that has been drawn together with using positron annihilation lifetime spectroscopy (PALS) and developing and applying a new type of hyphenated technique between fractionation (chromatography) and microscopy (atomic force microscopy) techniques. The outcome has provided a unique perspective regarding the complexity of the PDMS-PBCH copolymer morphology, which is believed to provide basis for a theoretical structure-properties relationship in this fascinating class of thermoplastic material. / AFRIKAANSE OPSOMMING: Polidimetielsiloksaan–poliëster (PDMS–PES) kopolimere lewer verbindings met goeie eienskappe en trek voordeel uit die unieke eienskappe van die twee baie verskillende komponente. Aangesien die aard van hierdie twee verbindings baie verskil het hulle ‘n gekompliseerde morfologie in die vastetoestand as gevolg van faseskeiding. Wanneer die poliëster komponent kristalliseerbaar is kan ‘n nog ryker variasie in morfologie verwag word. Die kettingstruktuur van die kopolimere in terme van die verspreiding van die verskillende segmente al langs die ketting en die variasie in samestelling, het ook ‘n groot invloed op die vastetoestandmorfologie. In hierdie studie is twee verskillende tipes poliëster gebruik om vyf reekse PDMS–PES gesegmenteerde kopolimere en een reeks vertakte PDMS–PES kopolimere te berei. Die twee poliëstersegmente is polibutileenadipaat (PBA) en polibutileensikloheksaankarboksilaat (PBCH). Die kopolimere is berei deur middel van polikondensasie in die smeltfase. Inligting aangaande verskeie faktore in the bereiding van die PDMS–PES kopolimere is ingewin. Die reekse kopolimere wat berei is, het dit moontlik gemaak om die invloed van die tipe poliëster, kettingargitektuur, grootmaatsamestelling, bloklengte, kristalliniteit en reaksiekondisies op die oppervlakte en interne morfologie te bestudeer. Die opmerklike verskille in the eienskappe van die kopolimere word toegeskryf aan die verskille in die kopolimeermorfologie in terme van die mikrofaseskeiding, kristalliniteit en vryevolume eienskappe. Hierdie verskille het ook veranderings in die oppervlakte samestellings en verwante oppervlakte eienskappe teweeggebring. Multifase morfologie, in alle PDMS–PES kopolimere en die tipe morfologie wat waargeneem is, is afhanklik van die PDMS inhoud, die PDMS segmentlengte en die graad van vertakking. Drie tipes morfologie is waargeneem: sferiese mikro-gebiede van PDMS in ‘n PES matriks, ‘n bikontinueerlike dubbele-diamant tipe en sferiese mikro-gebiede van PES in ‘n PDMS matriks. Sferiese gebiede van die PDMS is ook waargeneem in kopolimere met ‘n lae PDMS inhoud tussen die kristallyne poliëster lae. Die kompleksiteit van die PDMS–PBCH kopolimeermorfologie is verder ondersoek deur gebruik te maak van ‘n wye reeks eksperimentele data afkomstig van positronvernietigingsleeftydspektroskopie (PALS), gevolg deur die ontwikkeling en toepassing van ‘n nuwe soort gekoppelde tegniek – tussen fraksionering (chromatografie) en mikroskopie (atoomkragmikroskopie) tegnieke. Die resultate het ‘n unieke perspektief gegee wat betref die kompleksiteit van die PDMS–PBCH kopolimeermorfologie en dien as ‘n basis vir die teoretiese struktuur–eienskapverwantskap van hierdie interessante klas termoplastiese materiale.

Multivariate and multiblock data analysis involves useful methodologies for analyzing large data sets in chemistry, biology, psychology, economics, sensory science, and industrial processes; among these methodologies, partial least squares (PLS) and orthogonal projections to latent structures (OPLS®) have become popular. Due to the increasingly computerized instrumentation, a data set can consist of thousands of input variables which contain latent information valuable for research and industrial purposes. When analyzing a large number of data sets (blocks) simultaneously, the number of variables and underlying connections between them grow very much indeed; at this point, reducing the number of variables keeping high interpretability becomes a much needed strategy. The main direction of research in this thesis is the development of a variable selection method, based on variable influence on projection (VIP), in order to improve the model interpretability of OnPLS models in multiblock data analysis. This new method is called multiblock variable influence on orthogonal projections (MB-VIOP), and its novelty lies in the fact that it is the first multiblock variable selection method for OnPLS models. Several milestones needed to be reached in order to successfully create MB-VIOP. The first milestone was the development of a single-block variable selection method able to handle orthogonal latent variables in OPLS models, i.e. VIP for OPLS (denoted as VIPOPLS or OPLS-VIP in Paper I), which proved to increase the interpretability of PLS and OPLS models, and afterwards, was successfully extended to multivariate time series analysis (MTSA) aiming at process control (Paper II). The second milestone was to develop the first multiblock VIP approach for enhancement of O2PLS® models, i.e. VIPO2PLS for two-block multivariate data analysis (Paper III). And finally, the third milestone and main goal of this thesis, the development of the MB-VIOP algorithm for the improvement of OnPLS model interpretability when analyzing a large number of data sets simultaneously (Paper IV). The results of this thesis, and their enclosed papers, showed that VIPOPLS, VIPO2PLS, and MB-VIOP methods successfully assess the most relevant variables for model interpretation in PLS, OPLS, O2PLS, and OnPLS models. In addition, predictability, robustness, dimensionality reduction, and other variable selection purposes, can be potentially improved/achieved by using these methods.

No description available.

Hydrophilic/hydrophobic block copolymers as proton exchange membranes (PEMs) has become an emerging area of research in recent years. Three series of hydrophilic/hydrophobic, fluorinated/sulfonated multiblock copolymers were synthesized and characterized in this thesis. These copolymers were obtained through moderate temperature (~100°C) coupling reactions, which minimize the ether-ether interchanges between hydrophobic and hydrophilic telechelic oligomers via a nucleophilic aromatic substitution mechanism. The hydrophilic blocks were based on the nucleophilic step polymerization of 3,3′-disulfonated, 4,4′-dichlorodiphenyl sulfone with an excess 4,4′-biphenol to afford phenoxide endgroups. The hydrophobic (fluorinated) blocks were largely based on decafluoro biphenyl (excess) and various bisphenols. The copolymers were obtained in high molecular weights and were solvent cast into tough membranes, which had nanophase separated hydrophilic and hydrophobic regions. The performance and structure-property relationships of these materials were studied and compared to random copolymer systems. NMR results supported that the multiblock sequence had been achieved. They displayed superior proton conductivity, due to the ionic proton conducting channels formed through the self-assembly of the sulfonated blocks. The nano-phase separated morphologies of the copolymer membranes were studied and confirmed by atomic force microscopy. Through control of a variety of parameters, including ion exchange capacity and sequence lengths, performances as high, or even higher than those of the state-of-the-art PEM, Nafion, were achieved. / Ph. D.

The purity of the disulfonated monomer, such as 3,3"-disulfonated-4,4"-dichlorodiphenyl sulfone (SDCDPS), was very important for obtaining high molecular weight copolymers and accurate control of the oligomer's molecular weight. A novel method to characterize the purity of disulfonated monomer, SDCDPS, was developed by using UV-visible spectroscopy. This allowed for utiliziation of the crude SDCDPS directly in the copolymerization to save money, energy, and time. Three series of tert-butylphenyl terminated disulfonated poly(arylene ether sulfone) copolymers (BPSH35, 6FSH35, and 6FSH48) with controlled molecular weightsï¼ Mnï¼ , 20 to 50 kg·mol-1, were successfully prepared by the direct copolymerization method. The molecular weight of the copolymer was controlled by a monofunctional monomer tert-butylphenyl, and characterized by the combination of 1H NMR spectra and modified intrinsic viscosity measurements in NMP with 0.05 M LiBr, which was added to suppress the polyelectrolyte effect. The mechanical properties of the membranes, such as the modulus, strength and elongation at break, were improved by increasing the molecular weights, but water uptake and proton conductivities found insensitive to copolymers" molecular weights. Three series of disulfonated poly(arylene ether ketone) random copolymers have been synthesized and comparatively studied, according to their different chemical structures, for use as proton exchange membranes. The copolymers containing more flexible molecular structures had higher water uptake and proton conductivity than the rigid structures at the same ion exchange capacity. This may be due to the more flexible chemical structures being able to form better phase separated morphology and higher hydration levels. A new hydrophobic-hydrophilic multiblock copolymer has been successfully synthesized based on the careful coupling of a fluorine terminated poly(arylene ether ketone) (6FK) hydrophobic oligomer and a phenoxide terminated disulfonated poly(arylene ether sulfone) (BPSH) hydrophilic oligomer. AFM images and the water diffusion coefficient results confirmed that the multiblock copolymer formed better proton transport channels. This multiblock copolymer showed comparable proton conductivity and fuel cell performance to the Nafion® control and had much better proton transport properties than random ketone copolymers under partially hydrated conditions. This suggested that the multiblock copolymers are promising candidates for proton exchange membranes especially for applications at high temperatures and low relative humidity. / Ph. D.

Poly(arylene ether sulfone)s (PAES) are important commercial polymers and have been extensively studied due to their excellent thermal and mechanical properties. However, some applications are still limited when good solvent resistance and low thermal expansion coefficient are required. There has been a continuous interest in developing new PAES based on new monomers or polymer modifications to obtain new properties or to enhance existing properties. In this dissertation, the synthesis, characterization and structure-property relationship of new 1,4-cyclohexylene ring containing PAESs were comprehensively studied. Different polymerization techniques were used to synthesize polymers with different segmental lengths. The monomer, 4,4'-[trans-1,4-cyclohexanebis(methylene)] bisphenol (CMB), was synthesized and fully characterized. Based on 4,4′-dihydroxy-p-terphenyl (DHTP), 4,4′-dihydroxybiphenyl (DHBP) and the CMB monomer, homopolymer and random copolymers of PAES were prepared with high molecular weights and high glass transition temperatures. Dynamic mechanical analysis (DMA) on these polymers showed multiple sub-Tg relaxations. A large increase in the ultimate elongation was obtained with the CMB and DHTP containing sample, which could be due to the strong sub-Tg relaxations observed from the DMA results. A series of four acid chloride monomers were synthesized and polymerized with phenol terminated PAES oligomers. Solution polymerization and pseudo-interfacial polymerization techniques were used to prepare both bisphenol-A (bis-A) based and DHBP based PAES oligomers. With the incorporation of the trans-1,4-cyclohexylene units, decreases in the glass transition temperatures were observed from both the bis-A based and the DHBP based polymers. However, melting transitions were only observed in the DHBP based trans-1,4-cyclohexylene containing PAESs. Crystallinity was confirmed by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). A mechanical property study of the high molecular weight trans-1,4-cyclohexylene containing polymer samples showed moderate ultimate elongation enhancements. A series of PAES-polyester multiblock copolymers were synthesized with both solution method and melt polymerization. In the solution method, phenol terminated PAES oligomers and the acid chloride terminated poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) oligomers were presynthesized and coupled in solution. The molecular weights of the polymer products obtained from the solution method were limited by solubility issues. Melt phase polymerization was employed to obtain high molecular weight polymers. Hydroxy ethoxy terminated PAES oligomers were synthesized and polymerized with 1,4-cyclohexanedimethanol (CHDM) and dimethyl terephthalate (DMT) in the melt. Polymers with high molecular weights were obtained. Tensile test results suggested that the mechanical properties of these polymers were dominated by the PAES components with polyester contents up to 20 wt%. Melting transitions were observed from polymers with higher polyester contents, and these polymers exhibited limited solubility in common organic solvents. / Ph. D.

Proton exchange membrane fuel cells (PEMFCs) have been extensively studied as clean, sustainable and efficient power sources for electric vehicles, and portable and residential power sources. As one of the key components in PEMFC system, proton exchange membranes (PEMs) act as the electrolyte that transfers protons from the anode to the cathode. The state-of-art commercial PEM materials are typically based on perfluorinated sulfonic acid containing ionomers (PFSAs), represented by DuPont's Nafion®. Despite their good chemical stability and proton conductivity at high relative humidity (RH) and low temperature, several major drawbacks have been observed on PFSAs, such as high cost, high fuel permeability, insufficient thermo-mechanical properties above 80°C, and low proton conductivity at low RH levels. Therefore the challenge lies in developing alternative PEMs which feature associated ionic domains at low hydration levels. Nanophase separated hydrophilic-hydrophobic block copolymer ionomers are believed to be desirable for this purpose Three series of hydrophobic/hydrophillic, partially fluorinated/sulfonated multiblock copolymers were synthesized and characterized in this thesis. The hydrophilic blocks were based upon the nucleophilic step polymerization of 3, 3′-disulfonated, 4, 4′-dichlorodiphenyl sulfone (SDCDPS) with an excess 4, 4′-biphenol (BP) to afford phenoxide endgroups. The partially fluorinated hydrophobic blocks were largely based on 4, 4′-hexafluoroisopropylidenediphenol (6F-BPA) and various difluoro monomers (excess). These copolymers were obtained through moderate temperature (~130-150°C) coupling reactions, which minimize the ether-ether interchanges between hydrophobic and hydrophilic telechelic oligomers via a nucleophilic aromatic substitution mechanism. The copolymers were obtained in high molecular weights and were solvent cast into tough membranes, which had nanophase separated hydrophilic and hydrophobic regions. The performance and structure-property relationships of these materials were studied and compared to random copolymer systems. NMR results supported that the multiblock sequence had been achieved. They displayed superior proton conductivity, due to ionic, proton conducting channels formed through the self-assembly of the sulfonated blocks. The nano-phase separated morphologies of the copolymer membranes were studied and confirmed by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Through control of a variety of parameters, including ion exchange capacity and sequence lengths, performances as high, or even higher than those of the state-of-the-art PEM, Nafion®, were achieved. Another series of semi-crystalline hydrophobic poly(ether ether ketone)-hydrophilic sulfonated poly(arylene ether sulfone) (PEEK-BPSH100) multiblock copolymers was first synthesized and characterized. However due to their semi-crystalline structure, PEEK blocks are insoluble in most organic solvents at relatively low reaction temperatures, which prevents the coupling reaction between PEEK and BPS100. In order to facilitate the synthesis and processing, removable bulky ketimine was introduced to synthesize amorphous pre-oligomers poly(ether ether ketimine) (PEEKt). The synthetic procedure first involves the synthesis of hydrophobic poly(ether ether ketimine)-hydrophilic sulfonated poly(arylene ether sulfone) (PEEKt-BPS100) multiblock pre-copolymers via coupling reactions between phenoxide terminated hydrophilic BPS100 and fluorine terminated hydrophobic PEEKt blocks. The membranes cast from PEEKt-BPS100 were boiled in 0.5M sulfuric acid water solution to hydrolyze the amorphous PEEKt blocks to semi-crystalline PEEK blocks and acidify BPS100 blocks to BPSH100 blocks simultaneously. FT-IR spectra clearly showed the successful hydrolysis and acidification. The proton conductivity, water uptake and other membrane properties of the acidified semi-crystalline PEEK-BPSH100 membranes were then evaluated and compared with those of the state-of-the-art PEM, Nafion®. / Ph. D.

Pour garantir au consommateur des aliments sûrs, l'emploi d'anabolisants chez les animaux de production est prohibée au sein de l'Union Européenne depuis la fin des années 1980. Bien que performantes, les méthodes de contrôle classiques ciblées font face à de nouveaux défis auxquels des stratégies alternatives (non ciblées),visant à identifier des biomarqueurs métaboliques caractéristiques de l'effet associé à ces pratiques, offrent des solutions innovantes. Le lipidome en particulier constitue une fraction d'intérêt pour l'étude des effets liés aux agents de répartition. La Spectrométrie de Masse (SdM) et la Résonance Magnétique Nucléaire (RMN) sont alors classiquement utilisées, indépendamment. Ce travail propose d'évaluer leur combinaison, bénéficiant des niveaux d'information différents associés, et les conséquences en termes de gain de prédiction ou d'identification des biomarqueurs. Comme modèle d'étude, des échantillons sanguins provenant d'animaux traités avec un agent de répartition connu pour perturber les profils lipidiques,ont été caractérisés. L'analyse du lipidome sérique par SdM a impliqué trois plateformes offrant des angles de vue différents afin de fournir une couverture étendue; l'étude de leur cohérence et complémentarité constituant l'un des objectifs de cette thèse. En parallèle, l'analyse par RMN a requis le développement d'une procédure complète, de l'optimisation des conditions de préparation d'échantillon aux paramètres d'acquisition, incluant des approches de RMN 2D rapides récentes. Enfin, le verrou associé à l'analyse des données issues des différentes sources a permis d'évaluer des approches statistiques innovantes, notamment multibloc. / Ln order to ensure safe food products for the consumer, the use of growth promoters in livestock farming has been prohibited in European Union since the end of the 80s. Although efficient, the conventional targeted control methods face new challenges to which alternative strategies (untargeted), aiming at identifying metabolic biomarkers characteristic of the effects induced by such practices, provide innovative solutions. In particular, the lipidome is an area of interest to investigate the effects associated with repartition agents. Mass Spectrometry (MS) and Nuclear Magnetic Resonance (NMR) are then classically used independently. This PhD work intends to evaluate their combination benefiting from the different levels of associated information and the consequences in terms of enhanced prediction or biomarker identification. As a study model, blood samples from animals treated with a repartition agent known to disrupt lipid profiles were characterized. The investigation of the serum lipidome with MS involved three distinct platforms providing different outlooks in order ta generate extended coverage; the study of their consistency and complementarity constituting one of the objectives of this PhD. In parallel, the analysis with NMR prompted the development of a complete workflow, from the optimization of the sample preparation conditions to acquisition parameters -including recent fast 2D NMR approaches. Finally, the challenge associated with the analysis of data from multiple sources allowed ta evaluate innovative statistical approaches such as multiblock analysis.

L'objectif de cette thèse est le développement d'une analyse rapide pour la caractérisation des produits lourds du pétrole. Des modèles de prédiction de propriétés des produits lourds ont été développés à partir des spectroscopies moyen infrarouge (MIR) et proche infrarouge (PIR). Ce travail a principalement porté sur l'optimisation des modèles prédictifs des teneurs en composés saturés, aromatiques, résines et asphaltènes (SARA). Une optimisation simultanée par algorithmes génétiques du choix des prétraitements des données spectrales et des variables à sélectionner a été évaluée. Cette approche a permis de conduire au meilleur pouvoir prédictif des modèles PIR et a montré le potentiel d'interprétation des variables sélectionnées. Une étude de comparaison des modèles développés séparément à partir des spectres MIR et PIR a ensuite été réalisée. La spectroscopie PIR s'est révélée être globalement plus performante dans le cadre de notre application. Il a également été démontré que la fusion de données spectroscopiques pouvait améliorer la qualité des prédictions. Au vu des résultats, il semble nécessaire que les modèles développés séparément à partir de ces spectroscopies conduisent à des performances similaires pour espérer une amélioration lors de la fusion des données spectrales. Le potentiel de l'interprétation des techniques de régression à blocs multiples a également été confirmé pour identifier les informations spectrales spécifiques contenues dans les spectres MIR et PIR. Enfin, les modèles de prédiction de la densité, des teneurs en SARA, en carbone Conradson, en hydrogène, en soufre et en azote ont été jugés satisfaisants pour une utilisation au laboratoire.