As new family of composite materials, polyrotaxanes, polymers containing rotaxane units, have interested scientists world wide in last few decades because of their new properties. Crown ethers have been widely used as the cyclic component in various polyrotaxanes. However, due to significant loss of threaded cyclic during polymerization, the driving force for threading remains unidentified. To prevent threaded cyclics from slipping off the backbone during polycondensation, a diol blocking group (BG) and a diacid chloride BG were prepared and incorporated into polyesters as monomers or comonomers. Using these BG's effectively reduced or prevented dethreading and thus indeed increased threading efficiency (m/n, average number of cyclics per repeat unit). The study also brought about new evidences for the formation of the polyrotaxanes, i.e., the hydrolytic recovery of threaded crown ether, different chemical shift of the threaded cyclic from the free species and nuclear Overhauser effect spectroscopy (NOESY) correlation. The threading efficiencies increased with lower polymerization temperature and increasing feed ratio of the cyclic vs. diol monomer. H-bonding between the crown ether and the OH groups of the diol monomers was identified as the driving force for threading and detailed threading and dethreading mechanisms were revealed. Co-polyurethane rotaxanes were also prepared by polymerization of diol BG, tetra(ethylene glycol) and 4,4'-methylenebis(p-phenyl isocyanate) (MDI) using 30C10 as solvent. Compared to that with the polyester backbone, dethreading was slower with the polyurethane because of H-bonding of the threaded cyclics with the in-chain NH groups. Interestingly, as proved by proton NMR spectra, the cyclics were locked at the NH sites in chloroform but pushed away from the site in DMSO. Thus these polyurethane rotaxanes were solvent switchable molecular shuttles with controlled microstructures. Based on H-bonding theory, a new method for the preparation of polyrotaxanes, a melt threading process, was demonstrated by threading "42C14" onto a preformed polyurethanes. The properties of the resulting polyurethane rotaxanes depended on threading efficiency (m/n): the higher m/n was, the lower the Tg was but the higher the intrinsic viscosity was. Novel topological polymers, mechanically-linked branched and crosslinked poly(methyl methacrylate)s were synthesized by pendant group modification of a preformed poly(methacryloyl chloride) with 5-hydroxymethyl-1,3-phenylene-1,3-phenylene-32-crown-10 (hydroxymethyl BMP32C10). The rotaxane structure was directly proved by NOESY. The polycondensation of di(hydroxymethyl)-BMP32C10, tetra(ethylene glycol) and MDI afforded similar mechanically-linked polyurethanes. The branching points were manifested by the complexation of the polyurethane with paraquat. The polydispersities (PDI) and topologies (linear, branched and crosslinked) of these polymers were simply controlled by the polymerization conditions; this will ultimately afford polymers with different processibility (melt viscosity) and mechanical properties, e.g., the slippage of the cyclics along the backbone ensures a higher elongation. The complexation between a preformed polymeric crown ether and paraquat afforded a novel class of main chain polyrotaxanes. The continuous titration method afforded accurate estimates of the equilibrium constant, enthalpy and entropy changes and thus polyrotaxanes with certain m/n can be simply designed. Compared to the starting polymers, polyrotaxanes had higher viscosity, higher glass transition temperature and different solubilities. A concept for the preparation of reversible branched and/or crosslinked homo- or co-polymers was invented, which was demonstrated by preparation of a reversibly branched polymer by self-assembly of a preformed polymeric crown ether and a polyurethane bearing paraquat moieties. This concept can be applied to increase the compatibility and the interfacial interaction for polymer blends and construct reversible networks. The present work is supported by the Division of Materials Research, National Science Foundation, through individual investigator grant DMR-93-20196. / Ph. D.

Biodegradable polyesters are considered as one of the most cost effective and environmentally friendly solutions to waste-disposal problems associated with traditional thermoplastics. The technologies for converting the resins into useful items require knowledge about the rheological properties of these materials. Adequate rheological models are essential for the design and optimization of the process technologies. Rheological properties of two commercial biodegradable polyesters- poly(lactic acid) (PLA) and aliphatic-aromatic co-polyester (AAC) Ecoflex -have been investigated using parallel plate and capillary rheometers. Results from a study on the extrusion instabilities of biodegradable polymers are reported for the first time. The experimental studies found that the biodegradable polyesters exhibit pseudoplastic (shear-thinning) behaviour and the Cox-Merz rule is obeyed. A Cross model was proposed to describe their shear-thinning behaviour. The viscosity of both PLA grades is more temperature sensitive than the viscosity of Ecoflex. It was observed that the extensional viscosity of Ecoflex is larger than that of PLA and that the extensional viscosity of biodegradable polymers is similar to that of LLDPE. The experimental results indicate that biodegradable polymer melts slip at the die wall. It was observed that with increasing shear rate PLA exhibits sharkskin and gross melt fracture while Ecoflex exhibits only gross melt fracture. With regards to flow instabilities PLA behaves like linear polyolefins, however without exhibiting stick-spurt phenomenon. While Ecoflex behaves like branched LDPE, its gross melt fracture starts at higher values of wall shear stress than LDPE. Both biodegradable materials exhibit small extrudate swell: up to 28% for PLA and up to 34% for Ecoflex, which is comparable to that of rigid PVC. It was observed that biodegradable polymers substantially degrade during extrusion processing. It was also found that blending PLA and Ecoflex produced immiscible blends. Melts of these blends exhibited sharkskin and gross melt fracture at higher shear stresses than the neat resins. This effect was attributed both to degradation during blending and to some sort of lubricating effect. / Thesis / Master of Applied Science (MASc)

Les polyHIPEs sont des matériaux cellulaires obtenus par polymérisation d’émulsions concentrées appelées HIPEs « High Internal Phase Emulsions ». La phase continue de l’émulsion contenant les monomères est le siège de la polymérisation permettant la création de la matrice solide. La phase dispersée engendre la porosité. Les matériaux polyHIPEs sont généralement synthétisés par polymérisation radicalaire. La variété des monomères utilisables est donc ainsi limitée. La majorité des polymères à haute performances étant obtenus par polycondensation, il serait d’un grand intérêt d’élargir la gamme des matériaux poreux de type polyHIPEs disponibles en utilisant cette technique. L’objectif de ce travail consiste à synthétiser des matériaux polyHIPEs obtenus par polycondensation ou polyaddition et à les caractériser. Réaliser une réaction de polymérisation par étape au sein d’une émulsion concentrée représente un vrai défi car ce type de réaction requiert généralement des conditions opératoires peu compatibles avec la stabilité des émulsions concentrées. Dans le cadre de ce travail, nous nous sommes intéressés à la synthèse de polyHIPEs de type polyuréthane et polyester. L’homogénéité de la morphologie de ces matériaux a été étudiée en faisant varier un certain nombre de paramètres tels que : la nature de l’émulsion (aqueuse ou non-aqueuse, stabilisée par des tensioactifs ou des particules), la nature des catalyseurs et les techniques de polymérisation. Ce travail a permis d’accéder pour la première fois à des matériaux polyHIPEs de type polyuréthane et polyester. Les résultats obtenus ouvrent la voie au développement dans ce domaine. / PolyHIPEs are cellular materials obtained by polymerization within HIPEs « High Internal Phase Emulsions ». The polymerization occurs in the continuous phase of the emulsion allowing the creation of a solid matrix. The dispersed phase induces the porosity. PolyHIPEs are generally obtained by free-radical polymerization which restricts the choice of monomers. The majority of high performance polymers are obtained by polycondensation therefore it will be a great interest to enhance the variety of polyHIPEs available by using this technique. The objective of this work consists to synthetize polyHIPEs using polycondensation or polyaddition. Performing a step-growth polymerization within emulsion is a great challenge because this kind of reaction requires conditions generally incompatible with the stability of HIPEs. In the context of this work, we focused on the synthesis of polyurethane and polyester polyHIPEs. The homogeneity of the morphology of the materials was studied by varying several parameters, such: the nature of the emulsion (aqueous or non-aqueous, stabilized by surfactants or particles), the nature of the catalysts and the polymerization techniques. This work opens the access for the first time to polyurethane and polyester polyHIPEs. The results obtained are a starting point for further development in this field.

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

No description available.

Le poly(butylène succinate) (PBS) est un polyester aliphatique biodégradable dont les propriétés en font un bon candidat pour le remplacement des polyoléfines. De plus, ses deux monomères, l'acide succinique et le butane-1,4-diol, peuvent être issus de la biomasse via un procédé de fermentation de sucres. L'étude réalisée ici a été séparée en deux grandes parties : le PBS linéaire d'une part et le PBS branché d'autre part. La première partie montre que la cinétique de synthèse du PBS suit bien le modèle d'estérification établi par Flory. Par la suite, l'étude des propriétés physico-chimiques du PBS a permis de remonter à des paramètres comme la masse molaire critique d'enchevêtrement, le module du plateau caoutchoutique, l'énergie d'activation du PBS fondu ou encore les paramètres de l'équation Mark-Houwink-Sakurada. Une étude sur ses propriétés thermiques a permis de décrire l'évolution de son comportement en fonction de sa masse molaire. Enfin, le profil d'énergie potentielle de l'estérification entre l'acide succinique et le butane-1,4-diol a été tracé en utilisant un outil de chimie quantique. La seconde partie traite de l'étude de PBS branchés obtenus en employant des agents de branchement (polyols) pouvant être issus de la biomasse comme l'huile de ricin, le glycérol et le polyglycérol. La stratégie adoptée a été le couplage entre un oligomère PBS fonctionnalisé acide carboxylique et les agents de branchement. L'étude en présence d'huile de ricin a mis en avant les relations entre la structure, déterminée en SEC-Triple Détection, et les propriétés physico-chimiques du PBS branché. L'optimisation de la synthèse en présence de glycérol ou de polyglycérol a été abordée à partir de la méthode des plans d'expériences. Comparé à la méthode « un facteur à la fois », des résultats prometteurs et semblables à ce qui est rapporté dans la littérature ont été obtenus pour l'étude du PBS branché en présence de glycérol. / Poly(butylene succinate) (PBS) is a biodegradable aliphatic polyester whose properties make it a promising polymer for the replacement of polyolefins. Moreover, its two monomers, succinic acid and 1,4-butanediol, can be produced via a fermentation process of sugars. This study has been separated into two great parts: linear PBS on the one hand and branched PBS on the other hand. In the first part, kinetics of the PBS synthesis showed a good agreement with the esterification model of Flory. We determined some fundamental parameters of PBS like critical molecular weight of entanglement, the rubbery plateau modulus, the energy of activation of melt PBS and parameters of the Mark-Houwink-Sakurada relationship. We have also realized a study on the influence of the molecular weight on the thermal properties of PBS. Finally, we constructed the potential energy profile of the esterification between succinic acid and 1,4-butanediol through a quantum chemistry study. The second part dealt with the study of branched PBS in the presence of biosourced polyols like castor oil, glycerol and polyglycerol. These syntheses were realized between an acid-functionalized PBS oligomer and the branching agents. We put forward the relationships between the structure, determined by SEC-Triple Detection, and the physicochemical properties of branched PBS in presence of castor oil. Syntheses of branched PBS in presence of glycerol or polyglycerol were optimized with design of experiments technique. Promising and similar results from the literature were obtained in the case of branched PBS in presence of glycerol compared to the method of “one parameter at a time”.

No description available.

No description available.

Thermomonospora curvata is a thermophilic actinomycete hylogenetically related to Thermobifida fusca that produces extracellular hydrolases capable of degrading synthetic polyesters. Analysis of the genome of T. curvata DSM43183 revealed two genes coding for putative polyester hydrolases Tcur1278 and Tcur0390 sharing 61% sequence identity with the T. fusca enzymes. Mature proteins of Tcur1278 and Tcur0390 were cloned and expressed in Escherichia coli TOP10. Tcur1278 and Tcur0390 exhibited an optimal reaction temperature against p-nitrophenyl butyrate at 60°C and 55°C, respectively. The optimal pH for both enzymes was determined at pH 8.5. Tcur1278 retained more than 80% and Tcur0390 less than 10% of their initial activity following incubation for 60 min at 55°C. Tcur0390 showed a higher hydrolytic activity against poly(ε-caprolactone) and polyethylene terephthalate (PET) nanoparticles compared to Tcur1278 at reaction temperatures up to 50°C. At 55°C and 60°C, hydrolytic activity against PET nanoparticles was only detected with Tcur1278. In silico modeling of the polyester hydrolases and docking with a model substrate composed of two repeating units of PET revealed the typical fold of α/β serine hydrolases with an exposed catalytic triad. Molecular dynamics simulations confirmed the superior thermal stability of Tcur1278 considered as the main reason for its higher hydrolytic activity on PET.